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1 The Journal of

ARACHNOLOGY

OFFICIAL ORGAN OF THE AMERICAN ARACHNOLOGICAL SOCIETY

VOLUME 18

SUMMER 1990

NUMBER 1

THE JOURNAL OF ARACHNOLOGY

EDITOR: James E. Carico, Lynchburg College
ASSOCIATE EDITOR: Gary L. Miller, The University of Mississippi
EDITORIAL BOARD: J. E. Carrel, University of Missouri; J. A. Coddington,
National Museum of Natural History, Smithsonian Institution; J. C.
Cokendolpher, Texas Tech University; F. A. Coyle, Western Carolina
University; C. D. Dondale, Agriculture Canada; W. G. Eberhard, Universidad
de Costa Rica; M. E. Galiano, Museo Argentino de Ciencias Naturales; M. H.
Greenstone, BCIRL, Columbia, Missouri; N. V. Horner, Midwestern State
University; D. T. Jennings, NEFES, Morgantown, West Virginia; V. F. Lee,
California Academy of Sciences; H. W. Levi, Harvard University; E. A.

Maury, Museo Argentino de Ciencias Naturales; N. I. Platnick, American
Museum of Natural History; G. A. Polis, Vanderbilt University; S. E.

Riechert, University of Tennessee; A. L. Rypstra, Miami University, Ohio; M.
H. Robinson, U.S. National Zoological Park; W. A. Shear, Hampden-Sydney
College; G. W. Uetz, University of Cincinnati; C. E. Valerio, Universidad de
Costa Rica.

THE JOURNAL OF ARACHNOLOGY (ISSN 0161-8202) is published in
Spring, Summer, and Fall by The American Arachnological Society at Texas
Tech Press.

Individual subscriptions, which include membership in the Society, are $30.00
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PROOFS, REPRINTS, and CHARGES: Authors will receive a reprint order
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This publication is printed on acid-free paper.

Young, O. P. and G. B. Edwards. 1990. Spiders in United States field crops and their potential effect
on crop pests. J. Arachnol., 18:1-27.

SPIDERS IN UNITED STATES FIELD CROPS
AND THEIR POTENTIAL EFFECT ON CROP PESTS

O. P. Young1

Southern Field Crop Insect Management Laboratory
USDA-ARS, P. O. Box 346
Stoneville, Mississippi 38776 USA

G. B. Edwards

Florida State Collection of Arthropods
Division of Plant Industry
Fla. Dept. Agric. & Cons. Serv.

P. O. Box 1269

Gainesville, Florida 32602 USA

ABSTRACT

An analysis of 29 faunal surveys of spiders found in nine field crops in the United States indicates
the presence of 614 species in 192 genera and 26 families. These species represent 19% of the ca. 3311
species occurring in North America. Five families included 61% of the species reported in field crops:
Salticidae (89 spp.), Linyphiidae (78), Araneidae (77), Theridiidae (64), and Lycosidae (62).
Considerably more species have been observed in cotton (308 spp.), soybean (262), and alfalfa (233)
than in guar (52), rice (75), and grain sorghum (88). Intermediate numbers of species have been
observed in peanuts (131), corn (136), and sugarcane (137). The North American spider fauna is
estimated at the species level to be 59% web-spinners and 41% wanderers, while those reported from
field crops are estimated to be 44% web-spinners and 56% wanderers. These differences may be
attributable to guild characteristics associated with dispersal and ability to survive in disturbed
habitats. The 42 most frequently occurring spider species were considered in detail and demonstrated
that the active wandering guild comprised the largest portion (45%) of this group. Orb-web (21%),
sheet- web (19%), ambush-wander (10%), and web-matrix (5%) spiders represented other guilds. The
most frequently occurring species in field crops were Oxyopes salticus Hentz (Oxyopidae), Phidippus
audax (Hentz) (Salticidae), and Tetragnatha laboriosa Hentz (Araneidae). These three species are
prime candidates for augmentation and conservation in field crops or in adjacent habitats as part of a
strategy to increase predation on crop pests.

INTRODUCTION

As recently as 1984, a review of spiders as biocontrol agents was able to lament
the current failure to consider the potential of spiders in insect suppression
programs (Riechert and Lockley 1984). This same review pointed out that
generalist predators such as spiders can in certain situations limit exponential
increases in insect populations in both natural and agricultural systems. A more
recent review of an abundant spider in agroecosystems, Oxyopes salticus Hentz,
indicated the considerable potential of this species for suppressing insect pest

'Current address: USDA-APHIS-BBEP, 6505 Belcrest Road, Hyattsville, MD 20782 USA.

THE JOURNAL OF ARACHNOLOGY

populations in agroecosystems (Young and Lockley 1985). These reviews and
others increasingly point to the importance of spiders as part of a strategy of
Integrated Pest Management.

Any investigator, however, who wishes to examine the spider fauna in a field
crop faces an immediate problem. The identification of species ia a tortuous
process for the novice, and may be close to impossible for many taxonomic
groups and for immature spiders. There is no single reference available to identify
the approximately 3311 species in North America, and only one regional work
(New England) attempts to provide identification aids for all resident species
(Kaston 1981). The approximately 470 genera of spiders in North America can be
identified with the aid of Roth (1985). The most commonly used North American
identification manual for novices considers only 223 genera and, though
presenting generalized descriptions of many species, contains no species-level keys
(Kaston 1978). Thus the identification of spiders must be performed by (1) use of
generic revisions of a highly technical nature, many of which are outdated, (2)
comparison with reference collections, most of which are at major urban
museums and relatively inaccessible to the agricultural researcher, and (3)
consultation with an expert in spider taxonomy, the number of which may be less
than 20 in the United States and Canada. Several of these experts are retired or
nearly so; all are overworked and reluctant to process large lots of specimens.
These factors alone may have discouraged past research in the spider fauna in
agroecosystems; they continue to be impediments to present and future research.
In this regard it is noteworthy that two agricultural research groups in the United
States that actively publish surveys of field-crop spiders are fortunate to have in-
house taxonomic expertise (i.e., Dean and Eger 1986, Lockley and Young 1986).

We have failed to detect significant movement in the last 10 years toward
implementation of any pest suppression strategy in the United States that
specifically includes spiders as part of the suppression strategy, though the
TEXCIM model for cotton fleahopper -Heliothis suppression may be a recent
exception (Hartstack and Sterling 1988). One possible reason for the slow
progress may be due to minimal knowledge concerning the species composition,
densities, and distribution of spiders in field crops. In an attempt to facilitate the
use of spiders in insect suppression strategies, we here summarize 29 faunal
surveys of spiders found in field crops of the United States. We further evaluate
the quality of the data base, analyze and interpret the data, and suggest directions
for future research.

MATERIALS AND METHODS

The entomological-araneological literature was searched for surveys of spiders
in North American field crops. We restricted the database to surveys that
included the following information: (1) majority of spiders identified to species,
(2) degree of sampling effort specified, (3) method and diel period of sampling
specified, and (4) degree of taxonomic assistance indicated. Information from
items 2-4 was coded (Table 1) and placed as an annotation after each survey
citation (Appendix 2). This format provided criteria to evaluate survey quality.

The nomenclatural problems associated with such a compilation from 29
different sources were particularly difficult to overcome. Many surveys contained

YOUNG & EDWARDS— FIELD CROP SPIDERS

Table 1. — Summary of sampling methodologies utilized in 29 field-crop surveys of spiders. Values
represent descriptive statistics or number in each category.

A. Number of years of sampling

Range 1-10
Mean 2.7
Mode 1,3

B. Maximum number of months sampled

within a year
Range 3-12
Mean 6.2
Mode 4
Not indicated 4

C. Did sampling period

1. Dirunal 29

2. Nocturnal 6

D. Maximum no. fields sampled/ month

Range 1-40
Mean 8.8

Mode 3
Below mean 18
Not indicated 3

E. Methods of sampling

1. Sweep 20

2. Vacuum 1 1

3. Pitfall 18

4. Hand 16

5. Berlese 3

6. Dip net 1

7. Shake-cloth 7

F. Acknowledgment of taxonomic

assistance

1. Yes 17

2. No 12

species names that: (1) recently had been split into several species, or combined
with another species name, (2) were no longer valid, (3) belonged in a different
family or genus, or (4) were probable misidentifications. The resultant species list
is our best estimate of the correct names and placement of species. We followed
Roth (1985) as the most current source of information on placement and
acceptability of familial and generic names.

RESULTS AND DISCUSSION

Limitations of the data. — Most surveys of arthropods in field crops usually
focus on a particular pest or group of pests (e.g., Scott et al. 1983a). When non-
pest arthropods are collected they are typically recorded as “beneficials”, or the
most common ones may be determined to species (e.g., Scott et al. 1983b;
Parencia et al. 1980). This usually is not the case for spiders, which unfortunately
are often lumped together into one group (e.g., Smith et al. 1976), or at best
subdivided into functional groups (e.g., Lockley et al. 1979). Such generalized
categorizations may be due to the identification problems previously mentioned
and to the fact that arachnologists typically have not conducted faunal surveys in
field crops, preferring more undisturbed areas where spider populations are
usually larger and more diverse. The net result is a paucity of information about
spiders associated with field crops. Nevertheless, we obtained copies of 29 surveys
of field-crop spiders that met our criteria for inclusion. Only 12 of these surveys
were published in refereed journals; the remainder appeared in state scientific
societal or agricultural experiment station publications (12), or as unpublished
theses and dissertations (5).

Assessing the quality of the 29 manuscripts utilized in one analysis was
difficult, because established criteria for determination of quality were unavail-
able. Six parameters were chosen that we believe should be included when a
faunal survey is published: (1) number of years of sampling, (2) maximum
number of months sampled within a year, (3) diel sampling period, (4) maximum
number of fields sampled per month, (5) method of sampling, and (6)

THE JOURNAL OF ARACHNOLOGY

acknowledgement of taxonomic assistance. We then tabulated the manuscripts
within categories of each parameter (Table 1).

One survey was conducted over a ten-year period, another over six, whereas 22
surveys lasted three years or less. Surveys <3 years are not likely to demonstrate
long-term trends, but should be sufficient to detect most species in an area.
Although several surveys were conducted over an entire 12-month period each
year, a majority (17) lasted for only 3-6 months. In some cases this short time
represented the life-span of the crop, though usually survey duration coincided
with the period of crop maturity or with peak arthropod abundance. The number
of different sites (fields) sampled each month ranged from 1 to 40; half the
surveys included four or fewer sample sites. Small sample sizes may not detect
variability within and among sites and may distort the relationship of single-site
abnormalities to other more typical sites.

Considerable variability was apparent in the importance that investigators
placed on sampling effort and the methods employed; some surveys even failed to
mention sampling effort. Most surveys utilized a variety of collection methods,
though five surveys used only one method. When methods to obtain both foliage-
and ground-dwelling spiders were employed, total number of species obtained
were higher than in single-strata surveys. Only six collection programs included
methods that specifically obtained nocturnal specimens, though 18 programs
included a method (pitfall) that collected ground-dwelling forms both day and
night.

Twelve surveys failed to acknowledge taxonomic assistance from specialists.
Given the aforementioned difficulties in spider identification, the likelihood that a
non-specialist could correctly identify all specimens obtained in a faunal survey is
indeed remote. Finally, the variability in methodologies among the 29 surveys is
probably less than that of faunistic surveys of spiders in nonagricultural habitats
(see review in Young et al., 1989). We conclude that a hypothetical “high quality”
survey would employ several collection methods to sample both foliage- and
ground-dwelling spiders, day and night, 12 months of the year, for 3-5 years, and
at ten or more locations.

Spider fauna of nine agroecosystems. — Faunal surveys were obtained for nine
crop systems in the United States, though not all systems were equally surveyed
(Appendix 1). Grain sorghum, guar, and peanuts were surveyed only once,
whereas multiple surveys were obtained for rice (2), sugarcane (2), corn (2),
alfalfa (4), cotton (7), and soybean (9). Species richness of spiders among the nine
crop systems can be grouped into three levels. Cotton contained the most species
(< 308), with soybean (< 262) and alfalfa (< 233) in the same high diversity
group. Guar (< 52), rice (< 75), and grain sorghum (< 88) comprised the group
with the lowest number of species. An intermediate group was represented by
peanuts (< 131), corn (< 136), and sugarcane (< 137). The wide disparity in
numbers of spider species that occur in these crop systems can be attributed to
several factors. Those crops surveyed most frequently had the most species, which
suggests sampling bias. A more likely explanation, however, involves the
structural complexity of plants. The nine crop plants can be separated into two
groups based on growth form: (1) multiple-branching dicotyledonous forms
include alfalfa, soybean, cotton, peanuts, and guar; and (2) simple-branching
monocotyledonous forms include rice, grain sorghum, sugarcane, and corn. Given
the known positive correlation between plant structural complexity and numbers

YOUNG & EDWARDS— FIELD CROP SPIDERS

of associated spiders (Greenstone 1984; Hatley and MacMahon 1980; Uetz 1976),
it is not surprising that cotton, for instance, supports many more spider species
than rice. Two apparent exceptions to this trend, guar and peanut, may be due to
minimal sampling effort.

Considering all field-crop systems as a whole, the spider community is
dominated by only a few of the 48 families that occur in all North American
habitats. Species of 26 families occur in field crops; 5 families contained 61% of
the total field -crop species — Salticidae (89 spp.), Linyphiidae (78), Araneidae (77),
Theridiidae (64), Lycosidae (62). Conversely, 6 families were represented by only
1 species. Several genera were represented by large numbers of species in field
crops —Theridion (19 spp.), Lycosa (17), Xysticus (16), Dictyna (15), Phidippus
(14). However, of the 192 genera recorded from field crops, 105 were represented
by only 1 species (Table 2).

Relation of crop fauna to North American fauna. — Millions of acres annually
in North America are occupied by various crop systems. About 22% of the land
in the United States is devoted to cropland, with another 8% covered by roads,
parking lots, houses, factories, and other structures (Anon. 1987). The remaining
70% is comprised of pastures, rangeland, forests, and margins; these are the
sources of spider immigrants to field crops. About 3311 species of spiders in 470
genera and 48 families are found in North America (Roth 1985) (Table 2). Fifty-
four percent of the families, 41% of the genera, and 19% of the species also occur
in field crops. At least one exhaustive field survey of the spiders of an entire
county indicates that these values for North America may be representative of
much smaller areas, as 19% of the species collected in Washington Co.,
Mississippi, also occurred in field crops (Young et al 1989).

The ten largest families of spiders in North America comprise 84% of the total
number of species. Some of these families, however, are poorly represented in
field crops (Table 2). Only 7% of the 252 agelenid species are associated with field
crops; likewise 9% of the 845 linyphiid species and 11% of the 159 dictynid
species occur in field crops. Conversely, several families are well represented in
field crops, e.g., 40% of the 192 araneid species, 31% of the 288 salticid species,
and 31% of the 128 thomisid species. Several factors may account for these
considerable differences between families. The most difficult spiders to identify
are the small-sized species of Linyphiidae. Some faunal surveys avoid this
problem by assigning linyphiids to one undifferentiated category, i.e., Erigoninae.
Thus, many more species of Linyphiidae likely occur in field crops than are
recognized or reported, particularly given their strong aerial dispersal
characteristics (Greenstone et al. 1987). Conversely, three of the taxonomically
better known spider families - Araneidae, Thomisidae, and Salticidae - are well
represented in field crops and known to be strong aerial or ground dispersers
(Greenstone et al. 1987; Young, unpubl. data).

One might expect a larger percentage of the total North American spider fauna
to occur in field crops. That such apparently is not so suggests that a selection
process is occurring, where only certain spider characteristics lead to increased
likelihood of occurrence in field crops. These characteristics probably are
associated with dispersal and subsequent survival in a highly disturbed and
sometimes noxious environment.

Prey-capturing guilds. — Functionally, spider families can be categorized on the
basis of prey capture method, e.g., web-spinning or wandering species (Table 2).

THE JOURNAL OF ARACHNOLOGY

Table 2. — Proportions of genera and species of North American spiders that occur in field crops,
a = genera and species data from Roth (1985), b = data from Gertsch (1979), Comstock (1940).
Percentages in parentheses.

Araneomorphae

Family

Genera

Species

Prey-capture

technique15

N. A.a

Field

crops

(%)

N. A.a

Field

crops

(%)

Agelenidae

(24)

252

(6.7)

Web-Sheet

Amaurobiidae

(12.5)

(1.2)

Web-Sheet

Anapidae

Web-Orb

Anyphaenidae

(100)

(35.1)

Wand-Active

Aphantochilidae

Wand-Ambush

Araneidae

(71.4)

192

(40.1)

Web-Orb

Caponiidae

Wand-Active

Clubionidae

(55)

193

(24.4)

Wand-Active

Ctenidae

Wand-Active

Desidae

Web-Sheet

Dictynidae

(33.3)

159

(11.3)

Web-Sheet

Diguetidae

Web-Matrix

Dinopidae

Web-Orb

Dysderidae

(66.7)

(28.6)

Wand-Active

Filistatidae

(33.3)

(7.6)

Web-Sheet

Gnaphosidae

(50)

248

(15.3)

Wand-Active

Hahniidae

(33.3)

(21.1)

Web-Sheet

Hersiliidae

Wand-Active

Homalonychidae

Want-Active

Hypochilidae

Web-Matrix

Leptonetidae

Web-Matrix

Linyphiidae

152

(21.1)

845

(9.2)

Web-Sheet

Loxoscelidae

Web-Sheet

Lycosidae

(62.5)

234

(26.5)

Wand-Active

Mimetidae

(100)

(53.8)

Wand-Ambush

Mysmenidae

(33.3)

(16.7)

Web-Orb

Nesticidae

(33.3)

(3.2)

Web-Matrix

Ochyroceratidae

Web-Sheet

Oecobiidae

(50)

(28.6)

Web-Sheet

Oonopidae

Wand-Active

Oxyopidae

(100)

(30)

Wand-Active

Philodromidae

(100)

(29.5)

Wand-Active

Pholcidae

(2)

(9.7)

Web- Matrix

Pisauridae

(50)

(64.3)

Wand-Active

Plectreuridae

Wand-Active

Salticidae

(73.3)

288

(30.9)

Wand-Active

Scytodidae

Wand-Active

Selenopidae

Wand-Ambush

Sparassidae

Wand-Ambush

Symphytognathidae

Web-Orb

Telemidae

Web-Sheet

Tengellidae

Web-Sheet

Theridiidae

(63)

231

(27.7)

Web-Matrix

Theridiosomatidae

Web-Orb

Thomisidae

(80)

128

(31.3)

Wand-Ambush

Uloboridae

(28.6)

(20)

Web-Orb

Zodariidae

Wand-Active

Zoridae

(100)

Wand-Ambush

Totals

470

192

(40.9)

3311

614

(18.5)

YOUNG & EDWARDS— FIELD CROP SPIDERS

Table 3. — Comparison of two prey-capturing guilds, web-spinning and wandering, for North
America and for field crops. Each family assigned to a guild based on data from Roth (1985), Kaston
(1981), Gertsch (1979), and Comstock (1940). Percentages in parentheses.

Web-spinning (%) Wandering (%)

N.A. fauna

Families

(52.1)

(47.9)

Genera

307

(65.3)

163

(34.7)

Species

1955

(59)

1356

(41)

Field crops

Families

(52)

(48)

Genera

(51)

(49)

Species

271

(44.1)

343

(55.9)

The North American spider fauna is estimated at the species level to be 59% web-
spinners and 41% wanderers (Table 3). The spider fauna of field crops, however,
is estimated to be 44% web-spinners and 56% wanderers. Such disparity between
the North American fauna and the field-crop fauna may be attributable to several
factors, which include dispersal (colonization) differences between guilds and
survival differences among disturbed (agricultural) habitats.

Dispersal differences between guilds.— Crop fields are assumed to be composed
of spider populations that have emigrated from adjacent habitats or are year-
round residents (Luczak 1979). Perennial crops such as alfalfa are more likely to
have over-wintering populations of spiders than annual crops such as wheat.
However, studies in England surprisingly have demonstrated that spider diversity
and density on enclosed land freshly plowed and cultivated in the autumn were
maintained until early spring as compared to similarly-treated land where spiders
were free to emigrate (Duffey 1978). Unfortunately, the ability of spiders to
survive autumnal crop harvest and subsequent soil disturbance has not been
investigated in the United States. Thus we are left with the assumption that
spiders immigrate each year from adjacent habitats into annual field crops, with
minimal overwintering in the crop field. Such immigration occurs aerially by
floating on silk threads (ballooning), or by silk-thread bridges between plants, or
by ambulatory movements on the ground (Gertsch 1979). Most of the spider
individuals that undergo aerial movement in field crops are araneids and
linyphiids, both families of web-spinners (Greenstone et al. 1987; Dean and
Sterling 1985). Wanderers, e.g., Salticidae and Lycosidae, comprised less than 9%
of the aeronauts in some investigations (Plagens 1986; Salmon and Horner 1977).
Crop fields and adjacent disturbed habitats may generate proportionately more
aerial dispersers than other habitats, because species that occupy these “unstable”
habitats have greater aeronautic dispersal powers (Greenstone 1982; Meijer 1977).

Survival differences between guilds. — Only those spider species with good
dispersal characteristics are likely to appear in a field crop. Their continued
presence in the crop, however, is due to other characteristics, such as their ability
to avoid predation, tolerate the typically hot and dry environment, adapt to the
particular plant structure and spatial pattern, and find food. In general, web-
spinners and wanderers exhibit differences in these abilities. Wandering spiders
contain few examples of feeding specialists, with most species capable of
capturing a wide diversity of prey types and sizes (Nentwig 1986). One of the

THE JOURNAL OF ARACHNOLOGY

most abundant spiders in field crops is a wanderer, Oxyopes salticus , which
consumes at least 34 species of insects in 21 families and nine orders (Young and
Lockley 1985). Web-spinners, however, exhibit considerable specialization on prey
types and sizes (Nentwig 1985). This suggests that wandering spiders may be more
likely to find suitable food than web-spinners in a field crop.

Habitat characteristics that are particularly important to web-spinners are plant
structure and spacing. Increased availability of substrate for web attachment is
usually associated with increased spider density (Rypstra 1983). Many of the
larger orb-weavers have specific habitat preferences for particular heights above
the ground and large distances between plants (Enders 1974). Such conditions
may occur in field crops for only short periods of time or not at all Sheet-web
and tangle-web weavers also have substrate requirements that infrequently are
available in field crops (Rypstra 1983). The movement through a crop field of
farming equipment associated with cultivation and chemical applications no
doubt damages a considerable proportion of the resident spider webs, but
probably has less effect on the wandering spiders. Factors associated with the
degree of food specialization, the structure of the habitat, and the differential
impact of disturbance may be sufficient to explain the relatively lower numbers of
web-spinning species in field crops.

Characteristics of the most frequently occurring spiders in field crops. — The 29

faunal surveys considered herein represent a geographic range from New York to
Florida to California and a plant-structural range from rice to soybean. Several
spider species occur over a wide geographic range and in a variety of crops.
Forty-two species (Table 4) are widely distributed among the crop systems
investigated thus far and probably represent the most abundant species found in
field crops. At least 1 / 3 of the 42 species average less than 4 mm in body length.
Such small spiders probably prey on the smaller pests such as thrips, aphids, and
inn natures of Heteroptera and Lepidoptera. The dispersal of the eight small-sized
liny p hud species (Table 4) is more affected by the unpredictability of air currents
than is that of the larger species (Greenstone et al 1987). Their capture in field
crops thus may indicate only recent accidental arrival and not necessarily
successful predatory activity. The largest guilds in this assemblage of 42 species
are the active wanderers (19 species) and the orb-web spiders (9 spp.), which
suggests that active wandering may be the most successful hunting strategy
employed by spiders in field crops. Three species — Tetragnatha laboriosa Hentz,
Oxyopes salticus , Phidippus audax (Hentz) — have been found in all nine crop
systems, usually were the most abundant predators in those crops, and are among
the most abundant spiders in North America (K. as i on 1978). Tetragnatha
laboriosa is a small orb-weaver that may leave its web to disperse or search for
food and is frequently captured in ground pitfall traps (Culin and Yeargan 1983).
Other members of the genus Tetragnatha actively seek prey away from the web in
ways similar to wandering spiders (Horn 1969). Oxyopes salticus is an active
wanderer more tolerant of hot and dry crop situations than some other common
predators of the southeastern United States (Mack et al. 1988), and was the
numerically dominant predator in several crop systems (Young and Lockley
1985). Phidippus audax is an active wanderer that is large (body length 8-15 mm),
hunts on foliage, often is locally abundant, consumes a wide range of prey sizes,
and occurs in many habitats (Roach 1987; Young 1989b). These three species — T
laboriosa , O. salticus , R audax — are prime candidates for population

YOUNG & EDWARDS— FIELD CROP SPIDERS

augmentation by releases of field-captured or lab-reared individuals, or for
population enhancement through habitat manipulations of field crops and
adjacent plant communities. As an example of their potential importance, P
audax and O. salticus are key predators of Heliothis spp. and the fleahopper
Pseudatomoscelis seriatus (Reuter) in cotton and adjacent habitats (Dean et al.
1987). By including field counts of these spiders in the TEXCIM cotton insect
management model, predictions of pest abundance and subsequent action
recommendations have been improved (Hartstack and Sterling 1988).

Prey of common crop-inhabiting spiders. — Prey choices have been documented
for several of the abundant species that occur in agroecosystems (Table 4).
Oxyopes salticus is known to capture the tarnished plant bug, Lygus lineolaris
(Palisot) (Young and Lockley 1988), the imported fire ant, Solenopsis invicta
Buren (Nyffeler et al. 1987a), the bollworm, Heliothis zea (Boddie) (Whitcomb
1967), and at least 15 other economically important field-crop pests (Young and
Lockley 1985). Crop pests consumed by P. audax , besides the three just
mentioned, include the spotted cucumber beetle, Diabrotica undecimpunctata
howardi Barber, the three-cornered alfalfa hopper, Spissistilus festinus (Say), the
boll weevil, Anthonomus grandis Boh., and numerous others (Young 1989b).
Pisaurina mira (Walck.) (Pisauridae) preys on these six crop pests and also
consumes the chinch bug, Blissus sp., the leafhopper Chlorotettix sp., the fall
armyworm, Spodoptera frugiperda (J. E. Smith), and a variety of other
arthropods (Young 1989c). These same crop pests are fed upon by many other
common species of wandering spiders, such as Metaphidippus galathea (Walck.)
(Salticidae), Misumenops spp. (Thomisidae), Peucetia viridans (Hentz)
(Oxyopidae), Pardosa milvina (Hentz) (Lycosidae), and Chiracanthium inclusum
(Hentz) (Clubionidae) (Plagens 1985; Howell and Pienkowski 1971; Whitcomb
and Bell 1964). Small web-spinning spiders such as T. laboriosa seem to capture
only small flies and aphids (Provencher and Coderre 1987; Whitcomb and Bell
1964), and spin a web that is easily destroyed by wind gusts (LeSar and Unzicker
1978). The common large orb-web spider, Argiope aurantia Lucas (Araneidae),
spins a strong web capable of capturing large pests such as grasshoppers and
scarab beetles, but mostly captures aphids and small flies (Nyffeler et al. 1987b).
Thus the various web-spinning spiders that do occur in field crops may have little
impact on the “medium-sized” crop pests such as plant bugs, boll weevils, and
leaf beetles, and on the non-flying pests such as lepidopterous larvae.

Implications for spiders in IPM programs. — Several management strategies
could have immediate positive impacts on spider populations in field crops and
lead to increased levels of predation on crop pests. For example, reductions in
both chemical applications and cultivation frequencies would kill fewer spiders
and destroy fewer webs. Deployment of mulches, non-disturbance of weed covers,
and strip planting of diverse crops all increase habitat diversity and consequently
would support a larger and more diverse spider community. Augmentation of
spider populations by placement of egg sacs in a field also may be feasible. If the
pest-management strategy involved reduction of pest numbers in adjacent
habitats, then perhaps the most efficient means for accomplishing this would be
to conserve and enhance spider populations in these adjacent habitats. Reduction
of mowing frequency and herbicide usage in crop margins, as well as the
enlargement of such areas, may also result in increased spider populations (e.g.,
Young 1989a). Of course the easiest tactic to implement is non-intervention, with

THE JOURNAL OF ARACHNOLOGY

Table 4. — Size ranges, hunting techniques, and habitats of the 42 most frequently occurring spiders
in U. S. agroecosystems, a = data from Kaston 1978, 1981.

Length No. crop

Taxon

of adult

$ (mm)a

Hunting

technique

Habitat & strata3

systems
(out of 9)

ANYPHAENIDAE

Aysha gracilis

6.4-7

Wand-Act

On foliage

ARANEIDAE

Acanthepeira stellata

7-15

Web-Orb

Tall grass, low bushes

Argiope aurantia

19-28

Web-Orb

Tall grass, gardens

Argiope trifasciata

15-25

Web-Orb

Tall grass, sunny

Cyclosa turbinata

4.2-5

Web-Orb

Bushes

Gea heptagon

4. 5-5. 8

Web-Orb

Low grass & forbs

Glenognatha foxi

Web-Orb

Meadows & wastelands,
low

Larinia directa

5-12

Web-Orb

Grass, sunny

Neoscona arabesca

5-12

Web-Orb

Tall grass, low bushes

Tetragnatha laboriosa

Web-Orb

Meadows, bushes, long
grass

CLUBIONIDAE

Chiracanthium inclusum

4.9-9. 7

Wand-Act

On foliage

Clubiona abbotii

4-5.4

Wand-Act

On foliage

Tr ache las deceptus

3. 4-4. 2

Wand-Act

Under loose tree bark,
rolled up leaves

LINYPHIIDAE

Eperigone tridentata

2.3

Web-Sheet

Under dead leaves in
woods

Erigone autumnalis

1.4-1. 7

Web-Sheet

Grass close to ground,
under leaves

Florinda coccinea

3.5

Web-Sheet

In grass

Frontinella pyramitela

3-4

Web-Sheet

Tall grass, bushes in
pine woods

Grammonota texana

Web-Sheet

Low grass & forbs

Meioneta micaria

1.9

Web-Sheet

Ground, low forbs

Tennesseellum formicum

1.8-2. 5

Web-Sheet

In dead leaves on forest
floor

Walckenaeria spiralis

2.5

Web-Sheet

Under dead leaves in
woods

LYCOSIDAE

Lycosa helluo

18-21

Wand-Act

Ground

Lycosa rabida

16-21

Wand-Act

Ground

Pardosa milvina

5. 2-6. 2

Wand-Act

Ground, herbs, low bushes

Pardosa pauxilla

4-4.5

Wand-Act

Ground

Schizocosa avida

10-15

Wand-Act

Ground

OXYOPIDAE

Oxyopes salticus

5. 7-6. 7

Wand-Act

Low bushes, herbs

PHILODROMIDAE

Tibellus oblongus

7-9

Wand-Act

Tall grass, bushes

PISAURIDAE

Pisaurina mira

12.5-16.5

Wand-Act

Tall grass, bushes

SALTICIDAE

Habronattus coecatus

5.5

Wand-Act

Ground, grass

Hentzia palmarum

4.7-6

Wand-Act

Tall grass, bushes & trees

Metaphidippus galathea

3. 6-5.4

Wand-Act

Tall grass, bushes

Metaphidippus protervus

3. 7-6. 3

Wand-Act

Tall grass, bushes

Phidippus audax

8-15

Wand-Act

Tree trunks, under stones,

bushes, tall grass, forbs

YOUNG & EDWARDS— FIELD CROP SPIDERS 1 1

Phidippus clarus

8-10

Wand-Act

Tall grass, bushes

Zygohallus rufipes

3-6

Wand-Act

Dead leaves on ground,

herbs, grass, low bushes

THERIDIIDAE

Latrodectus mactans

8-10

Web-Ma

Close to ground

Theridion murarium

2.8-4

Web-Ma

Trees, bushes, grass.

under stones

THOMISIDAE

Misumenoides

formocipes

5-11

Wand-Amb

Among flowers

Misumenops asperatus

4.4-6

Wand-Amb

In grass & foliage

Misumenops celer

5-6.7

Wand-Amb

Grassland flowers

Misumenops ohlongus

4. 9-6.2

Wand-Amb

Grass & weeds

no inputs of insecticides, biologicals, cultivations, or other manipulations. Non-
intervention allows natural enemies such as spiders to develop unimpeded by man
and exert natural controls over potential pest populations; such a tactic actually
works in many situations (Sterling et al. 1989).

Both theoretical and empirical studies have demonstrated that generalist
predators such as spiders can maintain prey populations at low densities (Post
and Travis 1979; Kajak 1978). The conservation and enhancement of generalist
(polyphagous) predators in field crops recently has been recommended (Luff
1983; Whitcomb 1981). Dean and Sterling (1987), however, point out the possible
negative impacts of spiders on other natural enemies of crop pests, and call for
detailed ecological studies to determine the roles of spiders in agroecosystems.
Nyffeler and Benz (1987), in a world-wide survey of spiders as natural control
agents, also point to the need for detailed ecological studies. Our review should
provide the basis for further investigations of field-crop spiders associated with U.
S. agroecosystems.

ACKNOWLEDGMENTS

The technical assistance of T. C. Lockley and M. S. Oltremari is gratefully
appreciated. An exceptionally thorough manuscript review was provided by D. T.
Jennings, with additional reviews by D. A. Dean, M. H. Greenstone, M. Nyffeler,
D. B. Richman, S. H. Roach, and W. L. Sterling.

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cotton in Texas. Texas Agric. Exp. Stn. Bull., 1566:1-8.

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predators on the cotton fleahopper and other prey. Southw. Entomol., 12:263-270.

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Duffey, E. 1978. Ecological strategies in spiders including some characteristics of species in pioneer
and mature habitats. Symp. Zool. Soc. London, 42:109-123.

Enders, F. 1974. Vertical stratification in orb-web spiders and a consideration of other methods of
coexistence. Ecology, 55:317-328.

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(Lycosidae: Pardosd). Florida Entomol., 65:83-89.

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vs. prey availability. Oecologia, 62:299-304.

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spiders in Missouri, USA, and New South Wales, Australia: Family and mass distributions. J.
Arachnol., 15:163-170.

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Texas Agric. Exp. Stn. Publ., MP-1646:l-38.

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and effect of harvest. J. Econ. Entomol., 64:163-168.

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Breymeyer and G. M. van Dyne, eds.). Cambridge Univ. Press, London.

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70:1-1020.

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Lockley, T. C, J. W. Smith, W. P. Scott and- C. R. Parencia. 1979. Population fluctuations of two
groups of spiders from selected cotton fields in Panola and Pontotoc Counties, Mississippi, 1977.
Southw. Entomol., 4:20-24.

Lockley, T. C. and O. P. Young. 1986. Prey of the striped lynx spider, Oxyopes salticus (Araneae,
Oxyopidae), on cotton in the Delta area of Mississippi. J. Arachnol., 14:395-397.

Luczak, J. 1979. Spiders in agrocoenoses. Pol. Ecol. Stud., 5:151-200.

Luff, M. L. 1983. The potential of predators for pest control. Agric., Ecosys., & Envir., 10:159-181.
Mack, T. P., A. G. Appel, C. B. Backman and P. J. Trichilo. 1988. Water relations of several
arthropod predators in the peanut agroecosystem. Environ. Entomol., 17:778-781.

Meijer, J. 1977. The immigration of spiders (Araneida) into a new polder. Ecol. Entomol., 2:81-90.
Nentwig, W. 1985. Prey analysis of four species of tropical orb weaving spiders (Araneae: Araneidae)
and a comparison with araneids of the temperate zone. Oecologia, 66:580-594.

Nentwig, W. 1986. Non-webbuilding spiders: Prey specialists or generalists? Oecologia (Berlin), 69:571-
576.

Nyffeler, M. and G. Benz. 1987. Spiders in natural pest control: A review. J. Appl. Entomol., 103:321-
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Nyffeler, M., D. A. Dean and W. L. Sterling. 1987a. Evaluation of the importance of the striped fynx
spider, Oxyopes salticus (Araneae: Oxyopidae), as a predator in Texas cotton. Environ. Entomol.,
16:1114-1123.

Nyffeler, M., D. A. Dean and W. L. Sterling. 1987b. Feeding ecology of the orb-weaving spider
Argiope aurantia (Araneae: Araneidae) in a cotton agroecosystem. Entomophaga, 32:367-375.
Parencia, C. R., W. P. Scott and J. W. Smith. 1980. Comparative populations of beneficial arthropods
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and 1978. Southw. Entomol., 5:22-32.

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function. Ph.D. Thesis, Univ. Florida, Gainesville.

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Entomol., 15:1225-1233.

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Theor. Biol., 79:547-553.

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Provencher, L. and D. Coderre. 1987. Functional responses and switching of Tetragnatha laboriosa
Hentz (Araneae: Tetragnathidae) and Clubiona pikei Gertsch (Araneae: Clubionidae) for the aphids
Rhopalosiphum maidis (Fitch) and Rhopalosiphum padi (L.) (Homoptera: Aphididae). Environ.
Entomol., 16:1305=1309.

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29:299-320.

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Salticidae). Environ. Entomol., 16:1098-1102.

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Rypstra, A. L. 1983. The importance of food and space in limiting spider web densities; a test using
field enclosures. Oecologia, 59:312-316.

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Arachnol., 5:153-157.

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diapause control insecticide treatments on predaceous arthropod populations in cotton fields. J.
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beneficial arthropod populations associated with cotton. Environ. Entomol., 5:435-444.

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Thomisidae), and Lygus lineolaris (Heteroptera: Miridae). J. Entomol. Sci., 24:252-257.

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arthropods associated with cotton. J. Entomol. Sci., 24:266-273.

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(Heteroptera, Miridae) and other arthropods. J. Arachnol., 17:43-48.

Young, O. P. and T. C. Lockley. 1985. The striped lynx spider, Oxyopes salticus (Araneae:

Oxyopidae), in agroecosystems. Entomophaga, 30:329-346.

Young, O. P. and T. C. Lockley. 1986. Predation of striped lynx spider, Oxyopes salticus (Araneae:
Oxyopidae), on tarnished plant bug, Lygus lineolaris (Heteroptera: Miridae): A laboratory
evaluation. Ann. Entomol. Soc. America, 79:879-883.

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Arachnol., 17:27-41.

Manuscript received February 1989, revised May 1989.

THE JOURNAL OF ARACHNOLOGY

APPENDIX 1

SPIDERS IN NINE AGROECOSYSTEMS OF THE UNITED STATES

For list of information sources. See Appendix 2.

Grain

Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

AGELENIDAE

Agelenopsis aperta (Gertsch)

A. emertoni Chamb. & I vie

A. kastoni Chamb. & Ivie

A. naevia (Walckenaer)

LA,MS

A. pensylvanica (C. L. Koch)

A. spatula Chamb. & Ivie

AL,AR

DE,KY

Agelenopsis sp.

Cicurina arcuata

FL,OH

FL,IA,IL

NY.VA

(Keyserling)

C. pallida Keys.

C. robusta Simon

Cicurina sp.

Coras medicinalis (Hentz)

C. perplexus Muma

Coras sp.

Cybaeus sp.

Tegenaria pagana C. L. Koch

Wadotes hybridus (Emerton)
AMAUROBIIDAE

Titanoeca sp.
ANYPHAENIDAE

Anyphaena celer (Hentz)

AL,TX

A. laticeps Bryant

A. maculata (Banks)

A. pectorosa L. Koch

Anyphaena sp.

DE,IA

Aysha decepta (Banks)

A. velox (Becker)

A. gracilis (Hentz)

AL,AR,

DE,FL

LA,MS,TX, IL

Aysha sp.

Oxysoma cubana Banks

Teudis mordax

(0. P.-Cambridge)

Wilfila saltabunda (Hentz)

AL,MS,TX

NY,VA

Wulfila sp.

ARANEIDAE

DE,KY

Acacesia hamata (Hentz)

AL,AR,TX

Acanthepeira cherokee Levi

A. stellata (Walck.)

OK,TX

AL,AR,

FL,IL,

KY,NY,VA

MS,TX

KY,LA,

MO,NC

A. venusta (Banks)
Acanthepeira sp.

DE,NC

Alpaida calix (Walck.)

Araneus guttulatus

(Walck.)

A. juniperi (Emerton)

A. marmoreus Clerck

A. miniatus (Walck.)

A. nordmanni (Thorell)

A. pegnia (Walck.)

A. pratensis (Emerton)

A. thaddeus (Hentz)

A. trifolium (Hentz)

NY.VA

Araneus sp.

FL,OH

DE,FL,

IA,KY,NC

KY»NY,VA

Araniella displicata (Hentz)

AL,AR,LA

NY.VA

Araniella sp.

Argiope aurantia Lucas

FL,OH

AR,TX

DE,IA,IL,

KY.LA.NC

A. trifasciata (Forskal)

FL.OH

AR,TX

FL,IL,

KY,NC

KY,NY,VA

YOUNG & EDWARDS— FIELD CROP SPIDERS

Grain Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

Argiope sp.

Cyclosa caroli (Hentz)

C. conica (Pallas)

C. turbinata (Walck.)

AR,TX

KY,VA

Cyclosa sp.

Eriophora ravilla

(C. L. Koch)

Eustala anastera (Walck.)

FL.OH

QK,TX

AL.AR.TX

E. cepina (Walck.)

Eustala sp.

Gasteracantha cancriformis

DE,KY

(L.)

Gea heptagon (Hentz)

AR.TX

AL,LA,TX

DE, FL,
KY,NC

KY,VA

Glenogn&tha foxi (McCook)

AR,TX

DE,IL,KY KY,NY,VA

Hypsosinga pygmaea
(Sundevall)

H. rubens (Hentz)

Larinia directa Hentz

MO,NC

Larinia sp.

Leucauge venusta (Walck.)

AR,LA

DE,FL,MO

Leucauge sp.

Mangora gibberosa (Hentz)

FL.OH

AR.TX

DE,NC

NY.VA

M. maculata (Keys.)

M. placida (Hentz)

M. spiculata (Hentz)

Mangora sp.

Mecynogea lemniscata

(Walck.)

Metazygia wittfeldae

AL,AR,TX

(McCook)

Metepeira labyrinthea

MS.TX

(Hentz)

AR,MS

Metepeira sp.

Micrathena gracilis (Walck.)

AL,AR,

MS.TX

M. sagittata (Walck.)
Micrathena sp.

Neoscona arabesca (Walck.)

AR,TX

FL.OH

AL,AR,

DE,FL,

KY,NY,VA

LA,MS,

IL,KY,LA,

MO,NC

N. domiciliorum (Hentz)

N. hentzii (Keys.)

N. oaxacensis (Keys.)

OK,TX

N. pratensis (Hentz)

N. utahana (Chamberlin)

Neoscona sp.

FL,MO,NC

Nephila clavipes (L.)

Nuctenea cornuta (Clerck)

N. sclopetaria (Clerck)
Nuctenea sp.

Pachygnatha autumnalis

Keys.

DE,KY

KY.VA

R tristriata C. L. Koch
Pachygnatha sp.

Scoloderus cordatus
(Taczanowski)

Tetragnatha caudata

KY,NY,VA

Emerton

T. elongate. (Walck.)

AL,AR,MS

; MO

T. laboriosa Hentz

AR,TX

FL.OH

OK.TX

AL,AR,

DE,FL,IA,

CA.KY,

LA,MS,TX

IL,KY,

T. pallescens F.O.P.-Camb.

T. straminea Emerton

AL,LA

T. versicolor Walck.

Tetragnatha sp.

FL,MO,NC

Verrucosa arenata (Walck.)

Wagneriana tauricornis

(O.P.-Camb.) FL

Wixia ectypa (Walck.) VA

THE JOURNAL OF ARACHNOLOGY

Grain Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

Wixia sp.

Zygiella dispar (Kulczynski)

CLUBIONIDAE

Agroeca pratensis Emerton

A. trivittata (Keys.)

Agroeca sp.

Castianeira alteranda Gertsch

C. amoena (C.L. Koch)

C. crocata (Hentz)

C. descripta (Hentz)

AL,AR

C. floridana (Banks)

C. gertschi Kaston

AL,TX

C. longipalpus (Hentz)

AL,AR

LA,TX

FL,LA

C. occidens Reiskind

C. variola Gertsch

Castianeira sp.

Chiracanthium inclusum

IA.KY

(Hentz)

AL,AR,

DE,FL,

MS,TX

IL,KY,NC

C. mildei L. Koch
Chiracanthium sp.

Cluhiona abbotii L. Koch

AL,AR,LA

DE,IL,

KY,NC

KY,NY,VA

C. catawba Gertsch

C. johnsoni Gertsch

C. kagani Gertsch

C. maritima L. Koch

C. obesa Hentz

C. pikei Gertsch

C. plumbi Gertsch

C. procteri Gertsch

C. pygmaea Banks

C. riparia L. Koch

C. saltitans Emerton

C. spiralis Emerton

Clubiona sp.

DE.IA,

KY,NC

Clubionoides excepta

(L. Koch)

Myrmecotypus lineatus
(Emerton)

Phrurotimpus alarius (Hentz)

P. borealis (Emerton)

P emertoni Gertsch

P. minutus (Banks)
Phrurotimpus sp.

Scotinella fratella (Gertsch)

S. pallida Banks

Scotinella sp.

Strotarchus piscatoria

(Hentz)

Syrisca afftnis (Banks)

Trachelas deceptus (Banks)

AR.LA.TX

FL,LA

T. similis F.O.P.-Camb.

T. tranquillus (Hentz)

AL,AR,MS

KY.NY

T. volutus Gertsch

Trachelas sp.

LA.TX

KY.NC

DICTYN1DAE

Argenna obesa Emerton
Dictyna annexa

Gertsch & Mulaik

D. bellans Chamberlin

D. bicornis Emerton

D. bostoniensis Emerton

D. consults Gertsch & Ivie

D. foliacea (Hentz)

D. hentzi Kaston

D. hoya Chamb. & Ivie

D. iviei Gertsch & Mulaik

D longispina Emerton

YOUNG & EDWARDS— FIELD CROP SPIDERS

Taxon

Grain

sorghum

Rice

Sugar-

cane

Corn

Guar

Peanuts

Cotton

Soybean

D. manitoba Ivie

D. reticulata Gertsch & Ivie

D. segregata Gertsch &

Mulaik

AR,LA,TX

D. sublata Hentz

D. volucripes Keys.

AL,AR,TX

Dictyna sp.

FL,OH

FL,KY

Tricholathys hirsutipes

(Banks)

DYSDERIDAE

Ariadna sp.

Dysdera crocata C. L. Koch

FILISTATIDAE

Kukukania hibernalis

(Hentz)

AR.TX

GNAPHOSIDAE

Cesonia bilineata (Hentz)

C. sincere Gertsch & Mulaik

Drassodes auriculoides

Barrows

D. gosiutus Chamberlin

AR.LA

Drassodes sp.

Drassyllus creolus

AL,TX

DE,KY

Chamb. & Gert.

D. depresses (Emerton)

D. fallens Chamberlin

IL,KY

D. gynosaphes Chamberlin

D. lepidus (Banks)

D. notonus Chamberlin

LA.TX

D. orgilus Chamberlin

Drassyllus sp.

AL, AR.TX

Gnaphosa fonlinalis Keys.

G. sericata (L. Koch)

Haplodrassus signifer

AR.TX

IL,KY

(C. L. Koch)

Haplodrassus sp.

Herpyllus ecclesiasticus

Hentz

Micaria aurata (Hentz)

M. triangulosa Gertsch

M. vinnula Gertsch & Davis

Micaria sp.

Nodocion floridanus (Banks)

N. rufithoracicus Worley
Sergiolus capulatus (Walck.)

S. lowelli Chamb. &

IL.NC

Woodbury

S. minutus (Banks)

S. ocellatus (Walck.)

Sergiolus sp.

Synaphosus paludis

(Chamb. & Gert.)

Urozelotes rusticus (L. Koch)
Zelotes duplex Chamberlin

Z. gertschi Platnick &

Shadab

Z. hentzi Barrows

AR,LA

Z. laccus (Barrows)

Z. pseustes Chamberlin

Z. subterraneus (C. L. Koch)
Zelotes sp.

FL,KY

HAHNIIDAE

Neoant istea agilis (Keys.)

IL.KY

N. mulaiki Gertsch

N. riparia (Keys.)

Neoantistea sp.

LINYPHIIDAE

Anibontes longipes

Chamb. & Ivie

Balhyphantes albiventris

(Banks)

Alfalfa

NY,VA

CA.VA

THE JOURNAL OF ARACHNOLOGY

Grain

Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

B. concolor (Wider)

B. palUdus (Banks)

Bathyphantes sp.

Centromerus cornupalpis

(O.P.-Camb.)

Centromerus sp.

Ceraticelus bryantae Kaston

C. creolus Chamberlin

C. emertoni (O.P.-Camb.)

C. formosus Cros. & Bishop

C. similis (Banks)

NY,VA

Ceraticelus sp.

Ceralinella placida Banks
Ceraiinops crenata Emerton

C. rugosa (Emerton)

Ceratinops sp.

Ceratinopsidis formosa
(Banks)

Ceratinopsis latkeps

(Emerton)

IL,KY

C. nigriceps Emerton

C. sutoris Cros. & Bishop
Ceratinopsis sp.

Collimia plumosus

(Emerton)

Eperigone albula

Zorsch & Crosby

K banksi Ivie & Barrows

K eschatologies (Crosby)

E. maculata (Banks)

E. tridenlata (Emerton)

KY,YA

E. trilobata (Emerton)
Eperigone sp.

Eridantes erigonoides

IL.KY

KY,VA

(Emerton)

KY,NY,VA

Erigone atm Blaekwall

B. autumnaiis Emerton

AR,TX

DE.FL,

IL,KY

KY,NY,VA

E barrowsi Crosby & Bishop

E. blaesa Crosby & Bishop

E. denligera O.P.-Cambridge

DE,KY

KY,NY

E. dentosa O.P.-Cambridge

E. praecwsa Chamb. & Ivie
Erigone sp.

Floricomus sp.

Florinda coccinea (Hentz)

AL,AR

DE,FL,

KY,MOsMC

Froniinella pyramiiela

(Walck.)

AL,AR,TX

DE.FL,

IL,KY

KY,VA

Gonatium rubens (Balckwall)
Grammonota capitaia

Emerton

G. inornata Emerton

DE,IL,KY KY,NY,VA

G. pictilis (O.P.-Camb.)

G. lexana (Banks)

Helophora sp.

Hypselistes Jflorens

AR/TX

(O.P.-Camb.)

Handiam jlaveola (Banks)
Lepthyphantes nebulosa

(Sundevall)

L. sabulosa (Keys.)
Lepthyphantes sp.

Linyphantes aeronauiicus

(Petrunk.)

Meioneta angulata (Emerton)
M. barrowsi Chamb. & Ivie

M. dactylata Chamb. & Ivie

M.fabra (Keys.)

DE,IL

M. maculata (Banks)

YOUNG & EDWARDS— FIELD CROP SPIDERS

Grain

Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

M. meridionalis

Cros. & Bishop

M. micaria (Emerton)

IL,KY

KY,VA

M. nigripes (Simon)

M. unimaculata (Banks)

IL,KY

KY,VA

Meioneta sp.

Microlinyphia mandibulala

AL,TX

NY,VA

(Emer.)

CA,NY,VA

M. pusilla (Sundevall)
Microneta sp.

1L,KY

Neriene clathrata Sundevall

N. maculate (Emerton)

AL,AR

N. radiate (Walck.)

Neriene sp.

Pimoa sp.

Scylaeceus pallidus (Emerton)
Spirembolus phylax

Chamb. & Ivie

Tapinocyba scopulifera
(Emerton)

Tennesseellum formicum

(Emerton)

AL,AR

DE,IL,

CA,KY,NY

Walckenaeria pallida

Emerton

W. puella Millidge

W. spiralis (Emerton)

1L,KY

CA,KY,NY,

LYCOSIDAE

Allocosa absoluta (Gertsch)

A. floridiana (Chamberlin)

A. funerea (Hentz)

AR,LA

DE,KY

KY,VA

A. mokiensis (Gertsch)

A. sublata (Montgomery)

Allocosa sp.

Arctosa littoralis (Hentz)

Arciosa sp.

Geolycosa riograndae

Wallace

Geolycosa sp.

Gladicosa gulosa Walck.

Lycosa acompa (Chamberlin)

L. ammophila Wallace

L. annexa Chamb. & Ivie

L. antelucana Montgomery

L. aspersa Hentz

L. baltimoriana (Keys.)

L. carolinensis Walck.

L. frondicola Emerton

L. georgicola Walck.

L. helluo Walck.

AR,LA,TX

DE,FL,

KY,LA

NY,NY,VA

L. lento Hentz

L. modesta (Keys.)

L. punctulata (Hentz)

AL,AR

DE,FL,NC

L. rabida Walck.

AL,AR,

DE,FL,

KY,VA

LA,TX

KY,NC

L. ripariola Bonnet

L. timuqua Wallace

Lycosa sp.

Pardosa atlantica Emerton/

DE,KY,NC

CA,KY

P. saxatilis (Hentz)

AR.TX

AL,AR

DE,IA,KY

KY,VA

P. delicatula Gert. & Wall.

LA,TX

P. distincta (Blackwall)

AL,LA,MS

MO,NC

P. littoralis Banks

P. mercurialis Montgomery

P. milvina (Hentz)

AR,TX

AL,AR,

DE,FL,

KY,NY,VA

LA,TX

IL,KY,

LA,NC

P. modica (Blackwall)

P. moesta Banks

THE JOURNAL OF ARACHNOLOGY

Grain

Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

P. montgomeryi Gertsch

P. parvula Banks

P. pauxilla Montgomery

AR,LA,TX

P. ramulosa (McCook)

Pardosa sp.

Pirata alachuus

Gert. & Wallace

P. allapahae Gertsch

P. insularis Emerton

P minutus Emerton

NY,VA

P. piraticus (Clerck)

P sedentarius Montgomery

P. seminola Gertsch &

Wallace

P. suwaneus Gertsch

P sylvanus Chamb. & Ivie

Pirata sp.

Schizocosa avida (Walck.)

AR,LA,TX

DE,KY

KY,VA

S. bilineata (Emerton)

DE,KY

KY,VA

S. crassipes (Walck.)

FL,KY

S. ocreata (Hentz)

AR,LA

DE,FL,LA

S. retrorsa (Banks)

Schizocosa sp.

Trabeops sp.

Trochosa avara (Keys.)

T. shenandoa Chamb. & Ivie

T. terricola (Thorell)

Trochosa sp.

MIMET1DAE

Ero leonina (Hentz)

Mimeius epeiroides Emerton

AR,MS

IL,KY,

KY,NY,V,

M. hesperus (Chamberlin)

M. nelsoni (Archer)

M. notius Chamberlin

M. puritanus Chamberlin
Mimetus sp.

AL,MS

DE,NC

MYSMENIDAE

Mysmena guttata (Banks)
NESTJCIDAE

Eidmannella pallida

(Emerton)

OECOBIIDAE

Oecobius cellariorum (Duges)
Oecobius sp.

OXYOPIDAE

Hamataliwa helia
(Chamberlin)

Oxyopes aglossus

Chamberlin

O. apollo Brady

O. salticus Hentz

AR,TX

AL,AR,

DE,FL,

CA,KY,V/

LA, MS

IA,IL,

KY,LA,

MO,NC,

O. scalaris Hentz

FL,IL

Peucetia viridans (Hentz)

AL,AR,

FL,LA,

MS,TX

PHILQDROMJDAE

Apollophanes texanus Banks
Ebo albocaudatus Schick

E. latithorax Keys.

E. pepinensis Gertsch

E. punctatus Sauer

& Platnick

Ebo sp.

Philodromus cespilum

(Walck.)

P. histrio (Latr.)

P. imbecillus Keys.

DE,IL

P. infuscatus Keys.

YOUNG & EDWARDS— FIELD CROP SPIDERS

Grain

Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

P keyserlingi Marx

P. marxi Keys.

P. minutus Banks

P. pernix BlackwaSl

P placidus Banks

P. pratariae (Schick)

P. rufus Walck.

P satullus Keys.

P vulgaris (Hentz)

Philodromus sp.

AR,IA

DE,KY,

KY,VA

Thanatus formicinus

(Clerck)

AL,LA,

T. rubicellus M. Leitas

T. striatus (C. L. Koch)

Thanatus sp.

Tibellus duttoni (Hentz)

T. maritimus (Menge)

AR,TX

T. oblongus (Walck.)

IA,IL,

CA,KY,

NY,VA

Tibellus sp.

DE,FL,NC

PHOLC1DAE

Pholcus phalangioides
(Fueselin)

Psilochorus redemptus

Gert. & Mulaik

Psilochorus sp.

PISAURIDAE

Dolomedes albineus Hentz

D. scriptus Hentz

D. tenebrosus Hentz

D. triton (Walck.)

AR,TX

AL,AR,

LA,TX

FL,MO

Dolomedes sp.

Pisaurina brevipes (Emerton)

P. dubia (Hentz)

P. mira (Walck.)

AL,AR,LA

DE,FL,

IL,KY

KY,NY

Pisaurina sp.

SALTICIDAE

DE,KY

Admestina tibialis (C. Koch)
Agassa cyanea (Hentz)

Ballus youngii

G. & E. Peckham

Corythalia canosa (Walck.)

Em aurantia (Lucas)

AL,AR,MS

FL,NC

E. militaris (Hentz)

AL,LA,

MS,TX

IL,KY,LA

E. pinea (Kaston)

Eris sp.

DE,MO

Euophrys sp.

Evarcha hoyi (G. & E.

Peckham)

Habrocestum pulex (Hentz)
Habrocestum sp.

LA, MS

Habronattus agilis (Banks)

AL,LA

H. borealis (Banks)

H. brunneus

AL,MS

(G. & E. Peckham)

H. calcaratus Banks

H. coecatus (Hentz)

AL,AR,

LA,MS,TX

LA,NC

CA,VA

H. decorus (Black wall)

H. mustaciatus

Chamb. & I vie

H. texanus (Chamberlin)

H. trimaculatus Bryant

H. viridipes (Hentz)

AL,LA,MS

Habronattus sp.

THE JOURNAL OF ARACHNOLOGY

Grain Sugar-

Taxon sorghum Rice cane

Hentzia mitrata (Hentz) LA

H. palmarum (Hentz) LA

Hentzia sp. OK

Lyssomanes viridis (Walck.)

Maevia inclemens (Walck.)

Marpissa bina (Hentz)

M. dentoides Barnes

M.formosa (Banks) TX

M. lineata (C. L. Koch)

M. pikei (G. & E. Peckbarn)

Marpissa sp.

Metacyrba taeniola (Hentz)

Metacyrba sp.

Metaphidippus castaneus
(Hentz)

M. exiguus (Banks)

M. galathea (Walck.)

M. insignis (Banks)

M. manni G. & E. Peckham

M. protervus (Walck.)

M. vitis Cockerell
Metaphidippus sp.

Neon sp.

Neonella vinnula Gertsch
Peckhamia americana
(G. & E. Peckham)

P. picata (Hentz) OK

Peckhamia sp.

Pellenes limatus
G. & E. Peckham
Phidippus apacheanus
Chamb. & Gert.

P. audax (Hentz) OK TX LA

P. cardinalis( Hentz)

P carolinensis
G. & E. Peckham

P. clams Keys. LA

P. insignarius C. L. Koch
P mystaceus (Hentz)

P. pius Schick
P. princeps
(G. & E. Peckham)

P pulcherrimus Keys.

P. purpuratus Keys.

P. putnami
(G. & E. Peckham)

P. regius, C. L. Koch
P. texanus Banks
Phidippus sp.

Phlegra fasciata ((Hahn)

Platycryptus undatus
(DeGeer)

Plexippus paykulli (Audouin)

Plexippus sp.

Salticus sp.

Sarinda hentzi (Banks) LA

Sassacus papenhoei
G. & E. Peckham OK

Sitticus cursor Barrows
S. dor sat us (Banks)

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

ALSAR,

DE,FL,NC

AL,AR,

DE,FL,

LA,MS,TX

IL,NC

DE,KY,NC

AL,TX

AL,LA

ar,la,

FL,IL,KY,

NY,VA

MS,TX

LA,MO,NC

AL,AR,TX

al,ar,

LA, MS

IA,IL

NY,VA

AR,TX

DE,FL,KY,

MO,NC

OK,TX

AL.AR,

FL,IL,

KY,NY,VA

LA,MS,TX

KY,LA,

MO,NC

AR,LA,TX

FL,OH

AL,AR,

FL,LA,

LA,MS,TX

MO,NC

AL,AR

QKJX

DE,FL,

IA,MO,NC

CA,KY,VA

AL,AR,

MS.TX

YOUNG & EDWARDS— FIELD CROP SPIDERS

Grain

Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

S. pubescens (Fabr.)

Sitticus sp.

Synageles sp.

Synemosyna formica

Hentz

AL,AR

Talavera minuta (Banks)
Thiodina puerpera (Hentz)

AL,AR,TX

T. sylvana (Hentz)

AL,MS,TX

FL,MO

Thiodina sp.

Tuteiina elegans (Hentz)

T. hard (Emerton)

Tuteiina sp.

Zygoballus nervosus

(G. & E. Peckham)

Z. rufipes

AR,TX

G. & E. Peckham

AL,AR,

MS,TX

DE,FL

Z. sexpunctatus (Hentz)

AL,LA,MS

FL,NC

Zygoballus sp.

IA,MO,NC

THERIDIIDAE

Achaearanea globosa (Hentz)

AL,AR,TX

A. tepidariorum (C. L. Koch)

Achaearanea sp.

Anelosimus studiosus (Hentz)
Argyrodes cancellatus

(Hentz)

A.fictilium (Hentz)

A. trigonum (Hentz)

Argyrodes sp.

Chrysso sp.

Coleosoma acutiventer (Keys.)

Coleosoma sp.

Crustulina sticta
(O.P.-Camb.)

Dipoena abdita

Gertsch & Mulaik

D. nigra (Emerton)

AR,LA,MS

Dipoena sp.

Enoplognatha marmorata

(Hentz)

E. ovata (Clerck)

Euryopis funebris

(Hentz)

AL,MS

KY,VA

E. gertschi Levi

E. texana Banks

Euryopis sp.

Latrodectus hesperus

Chamb. & Ivie

L. mactans (Fabr.)

AL,AR,CA

FL,KY,

LA,MS,TX

LA,NC

L. variolus (Walck.)
Paratheridula perniciosa

(Keys.)

R. fuscus Emerton

Robertus sp.

Steatoda albomaculata

AL,MS

(DeGeer)

S. americana (Emerton)

S. erigoniformis
(O.P.-Camb.)

S.fulva (Keys.)

S. grossa (C. L. Koch)

S. medialis (Banks)

S. quadrimaculaia

(O.P.-Camb.)

S. transversa (Banks)

5. triangulosa (Walck.)

Steatoda sp.

Theridion alabamense

ALJX

Gert. & Archer

THE JOURNAL OF ARACHNOLOGY

Grain

Sugar-

Taxon

sorghum

Rice

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

T. albidum Banks

DE,IL,

KY,NC

KY.VA

T. australe Banks

AR,TX

DE.KY

T. cheimatos Gert. & Archer

T. cinclipes Banks

T. crispulum Simon

T. differens Emerton

KY.NC

NY.VA

T. flavonotatum Becker

T. frondeum Hentz

AL,AR,MS

FL.IL,

KY.NY

T. glaucescens Becker

T. hidalgo Levi

T. llano Levi

T. lyricum Walck.

DE.KY

T. murarium Emerton

DE.NC

T. neshamini Levi

DE.IL.KY

KY.VA

T. pennsylvanicum Emerton

T. piclipes Keys.

FL.NC

T. rabuni Chamb. & Ivie

DE.IL

CA.VA

T. sexpunctatum Emerton

Theridion sp.

DE,KY,NC

Theridula emertoni Levi

DE.KY

T. opulenia (Walck.)

AL,AR,MS

FL.IL,

KY.NC

KY.VA

Thymoites expulsus
(Gert. & Mulaik)

T. unimaculalus (Emerton)

Thymoites sp.

Tidarren sisyphoides

(Walck.)

Tidarren sp.

THERIDIOSOMATIDAE

Theridiosoma gem mo sum

(L. Koch)

THOMISIDAE

Coriarachne floridana Banks

C. versicolor (Keys.)
Coriarachne sp.

AL,AR,LA

DE.NC

Misumena vatia (Clerck)

AL,MS

FL.IL,

KY.NC

Misumena sp.

Misumenoides formosipes

(Walck.)

QK,TX

AL.AR,

FL.IL,

NY.VA

MS,TX

KY.LA,

MO.NC

Misumenoides sp.

Misumenops asperatus

(Hentz)

AL,AR

FL.IA.IL

KY, NY.VA

MS,TX

KY.MO

M. celer (Hentz)

OK,TX

AL.AR,

MS.TX

FL.LA.NC

M. deserti Schick

M. dubius Keys.

M. lepidus (Thorell)

M. oblongus (Keys.)

AR,TX

AL.AR, LA,

CA.VA

MS.TX

Misumenops sp.

OK,TX

DE.KY,

MO.NC

Ozyptila conspurcaia

(Thorell)

O. creola Gertsch

O. monroensis Keys.

Ozyptial sp.

Synaema bicolor Keys.

S. parvula (Hentz)

AL.AR,

MS.TX

KY.NC

Synaema sp.

Tmarus angulatus (Walck.)
Trnarus sp.

MS.TX

NY.VA

Xysticus auctificus Keys.

AR.TX

IL.KY

KY.VA

X. bicuspis Keys. AL

YOUNG & EDWARDS— FIELD CROP SPIDERS

Taxon

Grain

sorghum

Rice

Sugar-

cane

Corn

Guar

Peanuts

Cotton

Soybean

Alfalfa

X. californicus Keys.

X. concursus Gertsch

X. discursans Keys.

KY,NY,VA

X. eiegans Keys.

AL,TX

X. ferox (Hentz)

1L,KY

X. fraternus Banks

X.funestus Keys.

AR.LA.TX

KY.NY

X. furtivus Gertsch

X. gulosus Keys.

X. luctans (C. L. Koch)

X. pellax O.P.-Camb.

X. texanus Banks

AR,TX

X. transversatus (Walck.)

X. triguttatus Keys.

KY,MO

KY,VA

Xysticus sp.

FL,OH

AL.MS

DE,IA,KY,

KY,VA

MO,NC

ULOBORIDAE

Hyptioles cava t us (Hentz)

Uloborus glomosus (Walck.)

AL.AR.LA

Uloborus sp.

ZORIDAE

Zora pumila (Hentz)

Totals = 614 taxonomic entries

137

136

131

308

262

233

THE JOURNAL OF ARACHNOLOGY

APPENDIX 2

Information sources for Appendix 1. Letter and number annotations refer to categories as listed in

Table 1.

GRAIN SORGHUM

OK Bailey, C. L. and H. L. Chada. 1968. Spider populations in grain sorghums. Ann. Entomol.
Soc. America, 61:567-571.

[A - 1; B - 4; C - 1; D - 1; E - 3,4,5; F - 2.]

RICE

AR Heiss, J. S. and M. V. Meisch. 1985. Spiders (Araneae) associated with rice in Arkansas with
notes on species compositions of populations. Southw. Natur., 30:119-127.

[A - 4; B - 3; C - 1; D - 9; E - 1,6; F - 1.]

TX Woods, M. W. and R. C. Harrel. 1976. Spider populations of a southeast Texas rice field.
Southw. Natur., 21:37-48.

[A - 1; B - 9; C - 1; D - 1; E - 1,3,4; F - 2.]

SUGARCANE

LA Ali, A. D. and T. E. Reagan. 1985. Spider inhabitants of sugarcane ecosystems in Louisiana:
An update. Proc. Louisiana Acad. Sci., 48:18-22.

[A - 3; B - ?; C - 1; D - ?; E - 1,2, 3,4; F - 1.]

LA Negm, A. A., S. D. Hensley and L. R. Roddy. 1969. A list of spiders in sugarcane fields in
Louisiana. Proc. Louisiana Acad. Sci., 32:50-52.

[A - 10; B - 6; C - 1,2; D - 8; E - 1,3,4; F - 2.]

CORN

FL Plagens, M. J. 1985. The corn field spider community: Composition, structure, development
and function. Ph.D. Thesis, Univ. Florida, Gainesville. 207 pp.

[A - 3; B - 12; C - 1; D - 6; E - 4; F - 1]

OH Everly, R. T. 1938. Spiders and insects found associated with sweet corn with notes on the
food and habits of some species. I. Arachnida and Coleoptera. Ohio J. Sci., 38:136-148.

[A - 1; B - 3; C - 1; D - 1; E - 4; F - 1.]

GUAR

OK, Rogers, C. E. and N. V. Horner. 1977. Spiders of guar in Texas and Oklahoma. Environ.
TX Entomol., 6:523-524.

[A - 3; B - ?; C - 1; D - ?; E - 1,3,4; F - 1.]

PEANUTS

TX Agnew, C. W., D. A. Dean and J. W. Smith, Jr. 1985. Spiders collected from peanuts and
non-agricultural habitats in the Texas west cross-timbers. Southw. Natur., 30:1-12.

[A - 3; B - 4; C - 1; D - 3; E - 1,3,4; F - 1.]

COTTON

AL, Skinner, R. B. 1974. The relative and seasonal abundance of spiders from the herb-shrub
MS stratum of cotton fields and the influence of peripheral habitat on spider populations. M.
S. Thesis, Auburn Univ., Alabama. 107 pp.

[A - 4; B - 3; C - 1; D - 27; E - 1,2; F - 2.]

AR Whitcomb, W. H. and K. Bell. 1964. Predaceous insects, spiders, and mites of Arkansas

cotton fields. Univ. Arkansas Agric. Exp. Stn. Bull., 690:1-84.

[A - 6; B - 5; C - 1,2; D - 4+; E - 1,2, 3, 4, 5; F - 2.]

CA Leigh, T. F. and R. E. Hunter. 1969. Predacious spiders in California cotton. California
Agric., 1969:4-5.

[A - 1; B - 12; C - 1,2; D - 3; E - 1,2,3, 4, 5; F - 2.]

LA Mysore, J. S. and D. W. Pritchett. 1986. Survey of spiders occurring in cotton fields in

Ouachita Parish, Louisiana. Proc. Louisiana Acad. Sci., 49:53-56.

[A - 1; B - 6; C - 1,2; D - 4; E - 1,3,4; F - 1.]

YOUNG & EDWARDS— FIELD CROP SPIDERS

MS Lockley, T. C., J. W. Smith, W. P. Scott and C. R. Parencia. 1979. Population fluctuations of
two groups of spiders from selected cotton fields in Panola and Pontotoc Counties,
Mississippi, 1977. Southw. EntomoL, 4:20-24.

[A -1; B - 4; C - 1; D - 30; E - 2; F - 2.]

TX Dean, D. A., W. L. Sterling and N. V. Horner. 1982. Spiders in eastern Texas cotton fields. J.
Arachnol., 10:251-260.

[A - 3; B - 5; C - 1; D - 1+; E - 1,2, 3, 4; F - 1.]

TX Kagan, M. 1943. The Araneida found on cotton in central Texas. Ann. EntomoL Soc.
America, 36:257-258.

[A - 2; B - ?; C - 1; D - 3; E - 4; F - 2.]

SOYBEAN

DE Culin, J. D., Jr. 1978. Spiders in soybean fields: Community structure, temporal distributions
of the dominant species, and colonization of the crop. M. S. Thesis, Univ. of Delaware,
Newark.

[A - 1; B -12; C - 1; D - 7; E - 3,7; F - 2.]

FL Hasse, W. L. 1971. Predaceous arthropods of Florida soybean fields. M. S. Thesis, Univ. of
Florida, Gainesville.

[A - 1; B - 4; C - 1; D - 12; E - 1,3,7; F - 1.]

FL Neal, T. M. 1974. Predaceous arthropods in the Florida soybean agroecosystem. M. S. Thesis,
Univ. of Florida, Gainesville.

[A - 3; B - 4; C - 1; D - 12; E - 1,2, 3,4, 7; F - L]

I A Bechinski, E. J. and L. P. Pedigo. 1981. Ecology of predaceous arthropods in Iowa soybean
agroecosystems. Environ. EntomoL, 10:771-778.

[A - 2; B - 4; C - 1; D - 15; E - 1,3,7; F - 2.]

IL LeSar, C. D. and J. D. Unzicker. 1978. Soybean spiders: Species composition, population
densities, and vertical distribution. Illinois Nat. Hist. Surv. Biol. Notes, 107:1-14.

[A - 2; B - 4; C - 1; D - 3; E - 1,2,7; F - 2.]

KY Culin, J. D. and K. V. Yeargan. 1983. Spider fauna of alfalfa and soybean in central
Kentucky. Trans. Kentucky Acad. Sci., 44:40-45.

[A - 3; B - 9; C - 1; D - 4; E - 3,7; F - 1.]

LA Goyer, R. A., D. W. Brown and J. B. Chapin. 1983. Predaceous arthropods found in soybean

in Louisiana. Proc. Louisiana Acad. Sci., 46:29-33.

[A - 1; B - 4; C - 1; D - 3; E - 1,3; F - 1.]

MO Bickenstaff, C. C. and J. L. Huggans. 1962. Soybean insects and related arthropods in
Missouri. Univ. Missouri Agric. Exp. Stn. Res. Bull., 803:1-51.

[A - 3; B - 4; C - 1; D - 21; E - 1; F - 2.]

NC Deitz, L. L., J. W. Van Duyn, J. R. Bradley, Jr., R. L. Rabb, W. M. Brooks and R. E.

Stinner. 1976. A guide to the identification and biology of soybean arthropods in North
Carolina. North Carolina Agric. Res. Serv. Tech. Bull., 238:1-264.

[A - 4; B - 4; C - 1; D - 40; E - 2,7; F - L]

ALFALFA

CA Yeargan, K. V. and C. D. Dondale. 1974. The spider fauna of alfalfa fields in northern
California. Ann. EntomoL Soc. America, 67:681-682.

[A - 3; B - 12; C - 1,2; D - 6+; E - 1,2, 3, 4; F - 1.]

KY Culin, J. D. and K. V. Yeargan. 1983. Spider fauna of alfalfa and soybean in central
Kentucky. Trans. Kentucky Acad. Sci., 44:40-45.

[A - 3; B - 10; C - 1; D - 4; E - 2,3; F - L]

NY Wheeler, A. G., Jr. 1973, Studies on the arthropod fauna of alfalfa V. spiders (Araneida).
Canadian EntomoL, 105:425-432.

[A - 4; B - 7; C - 1; D - 3; E - 1,3,4; F - 1.]

VA Howell, J. O. and R. L. Pienkowski. 1971. Spider populations in alfalfa, with notes on spider
prey and effect of harvest. J. Econ. EntomoL, 64:163-168.

[A - 2; B - 12; C - 1,2; D - 1; E - 1,2; F - 1.]

Edwards, R. L. and E. H. Edwards. 1990. Observations on the natural history of a New England
population of Sphodros niger (Araneae, Atypidae). J. Arachnol., 18:29-34.

OBSERVATIONS ON THE NATURAL HISTORY OF A
NEW ENGLAND POPULATION OF SPHODROS NIGER
(ARANEAE, ATYPIDAE)

Robert L. Edwards

Box 505

Woods Hole, Massachusetts 02543 USA
and

Eric H. Edwards

868 Teaticket Highway
East Falmouth, Massachusetts 02536 USA

ABSTRACT

The surface portion of the tube webs of Sphodros niger Hentz lies hidden at the interface between
duff and overlying pine needles in early successional pitch pine-oak woods on Cape Cod,
Massachusetts. Males search for females in June. Spiderlings hatch in August and leave the mother
the following April. Millipedes appear to be the principal food item. The surface tubes of older
juvenile spiders vary from 13 to 15 cm in length and tend down slope. The surface tube has the
consistency of thin parchment. The underground portion varies little in length, averaging 13 cm, and
is a simple cylinder. The only adult female web found had a surface tube 63 cm in length. This female
had at least 73 spiderlings.

INTRODUCTION

Since the revision of Sphodros by Gertsch and Platnick (1980), at which time
47 specimens of Sphodros niger Hentz were examined, the number of S. niger
specimens taken by various collectors has significantly increased (Beatty 1986;
Morrow 1986). Most of these new specimens are males, taken when they were
searching for females, usually during the month of June. One male was picked up
by Jonathan Coddington during the American Arachnological Society’s field trip
to Martha’s Vineyard in 1987. In this case the specimen was dead, found in the
web of a black widow spider. On the same day Vincent Roth and S. Beshers also
collected a male at Walden Pond, Mass. Carol Senske, daughter of the senior
author, collected a male on her property in Green Lane, Pennsylvania in early
June, 1984. Beginning in 1985 we have consistently picked up live males in the
Falmouth, Massachusetts area between the dates of 12 to 25 June. The objective
of this paper is to report on the results to date of our study of this elusive spider.

THE JOURNAL OF ARACHNOLOGY

RESULTS AND DISCUSSION

Habitat and web location. — We are aware of two concentrations of the species
in the southwestern corner of Cape Cod. Both are found in early successional
pitch pine ( Pinus rigida ) habitat with scattered white oaks ( Quercus alba) and
junipers ( Juniperus virginiana). The understory is variable, with only thinly
scattered grass under the pines in one area and a considerable amount of low
bush blueberry, scrub oaks, reindeer lichen (Cladonia sp.) and grass in the other.

A thorough search of the area for the tube webs followed the first capture of a
male in a pitfall trap in 1984. The search was unsuccessful. Further searches were
carried out following the observations reported by Beatty, op. cit. The open,
grassy areas in the woods were without webs. Almost by accident, a recently
vacated web was found in the woods, near where a male had been found (Fig. 1).
Efforts were redoubled following this find in and around the barer areas within
the woods, in circumstances where the spiders might have portions of their webs
under rocks, logs, tree roots, and other objects, again without success. Ultimately
we discovered that the preferred situation was one where there was a thick cover
of pine needles over duff, in generally bare areas and with the duff thick enough
to remain fairly moist through much of the summer. The above-ground capture
tubes lie underneath the needles and are therefore completely hidden from view.
The soil in this area is a coarse, sandy soil that retains little moisture. To say that
this spider is cryptic is an understatement.

Without exception the webs are on the slopes of gently rounded gullies, one to
three meters in elevation above the bottom. Webs were considerable distances
apart, averaging about 5 m from one another. No concentration such as that
described by Beatty (op. cit.) was observed. The majority found were those of
larger immature spiders (over 12 mm long). Only one unoccupied tube of a much
smaller individual was found, although the remnants of smaller tubes were twice
found attached to larger occupied tubes (Fig. 2).

Web architecture. — The webs of these immatures were more or less consistent
in their structure and length. In ten of the twelve tubes found so far, the surface
portion of the tube paralleled the duff-pine needle interface, averaged 13 cm in
length and invariably ran down slope. A relatively sharp, right angle turn led
down into the soil for a comparable distance, averaging about 13 cm. The other
two webs were found in thickets of low bush blueberries where there were no pine
needles but rather a year-round accumulation of leaves with leaf mold
underneath. The layout of the webs was otherwise just like those found in the
pine needles.

There is no obvious widening of the spider’s retreat at the bottom. Usually at
the very bottom a centimeter or more of compacted material had accumulated,
including Sphodros exuvia and a quantity of separated scutes of millipedes. The
surface portion of the tube (Fig. 4) has attached material comparable to that
found in the duff, while the subterranean section has a thin coating of soil. The
attached material is exactly what is external to the tube and may have become
attached as the web was constructed, not necessarily as a consequence of any
deliberate activity on the part of the spider. In our experience thus far with
captive S. niger , if the surface portion of the tube is left exposed, the spider
makes no attempt to disguise it and will eventually abandon it if left uncovered.

EDWARDS & EDWARDS— OBSERVATIONS ON SPHODROS NIGER

Figures 1-3. — Diagrams of the placement of Sphodros niger tube webs and burrows. 1, horizontal
portion partially under rotting board; 2, typical web of older juveniles; 3, gap indicates 32 cm of web
not shown.

The internal diameter of the horizontal tubes varies from 10 to 12 mm. This is
a roomy diameter considering the size of the spider. The inner surface of the
horizontal tube is a very light grey in color, smooth and parchment-like in
consistency and very strong. If carefully uncovered the tube retains its integrity.
The underground portion is soft and flexible, and fairly easily pulled apart. In
two cases, the horizontal portion separated from the vertical portion while the
pine needle cover was being pulled aside. The horizontal portion of the tube web
of an adult female with young, found in August 1988, was unexpectedly long (63
cm; Fig. 3). The vertical portion was exactly like all the others. The end of the
horizontal portion of the tube had been collapsed or drawn up by the spider and
was compacted into a fairly solid wad.

Behavior of captives. — At the time of this writing (January, 1989) we are
keeping several specimens in captivity. It is impossible to make direct
observations without disturbing them, since their natural cover has been
recreated; consequently we have made only limited behavioral observations.
Captive S. niger are quick to make new subsurface tubes, but do not reconstruct
the surface portion readily. If the subsurface portion of the original tube is placed
in a prefabricated hole with the horizontal portion attached and covered with
pine needles, the spider will use the entire tube. Those without horizontal tubes

THE JOURNAL OF ARACHNOLOGY

Figure 4. — The surface portion of the web of a mature female Sphodros niger, minus a 7-cm piece
and the underground section (13.5 cm). See text for details.

usually do a great deal of excavating, and piles of dirt soon appear at the surface
around the upper ends of their tubes. This behavior is reminiscent of an
observation of Beatty’s (op. cit.), in which he observed piles of dirt in and at the
end of a tube. At first this activity was puzzling, but eventually we concluded that
it usually preceded the construction of a new surface tube originating some
distance from the original point of entrance of the old tube into the ground. The
spider digs a new exit from below — it does not leave what web it has to start an
entirely new tube from the surface.

Webs were not found where the duff and leaf cover were thick enough to
encourage mice and shrews (esp. Blarina brevicauda and Sorex cinereus) to
forage and dig burrows. This could be as much a consequence of predation by
mammals as choice.

Food and feeding.— -These spiders seem to be little disturbed when removed
from their habitat if they are left in their tube. One spider almost immediately
seized and ate a small caterpillar that wandered across its tube while the web was
laid out in the bottom of a plastic pail, barely an hour after it had been removed
from its natural surroundings. Another juvenile spider, shortly after being placed
in its new home, opened its tube to toss out its shed exuvium.

Judging from the debris found in the bottoms of their tunnels, S. niger appears
to favor millipedes for food. A few beetle elytra were found as well. It is unlikely
that flies, caterpillars or other aerial and surface arthropods would have ready
access to the tube. The most abundant insects of any size in the duff-needle
interface are various species of carabid beetles, themselves predators. One carabid
genus Pterostichus sp., quickly caught and devoured a captive Sphodros that had

EDWARDS & EDWARDS— OBSERVATIONS ON SPHODROS NIGER

left its web. Another Pterostichus was found in an unoccupied web. There are a
few spiders, notably Steatoda americana (Emerton), Agelenopsis kastoni
Chamberlin & Ivie, and some lycosids in shallow retreats that occasionally are
found in small numbers at the duff-needle interface. Centipedes and sowbugs
occur here in fair number while millipedes are usually abundant. Earthworms are
infrequently observed in this situation but cannot be ruled out as potential prey.

Spiderlings. — The one female found with young on 14 August 1988, had 73
spiderlings in the horizontal portion of the web and an unknown number below
that in the vertical section. The spiderlings were transferred to the vertical portion
along with the adult and placed in an aquarium for observation and study. The
newly hatched spiderlings are unpigmented except for the eyes, well stocked with
yolk, and possess relatively underdeveloped limbs and spinnerets. In terms of
general body size and shape, the newly hatched spiderlings are slightly larger than
those that leave in the spring. In the wild the young leave the mother in April, at
which time they are moderately pigmented light brown in color, have become
more slender, look like miniature adults and measure from 2.5 to 2.6 mm. We
have yet to observe any ballooning activity on the part of the young — the few
captured in the wild were taken in a pitfall trap.

Behavior of males. — In any particular year males move about for
approximately a seven day period, but exactly when this activity occurs, is not
predictable. In 1984, 1985, and 1986, movement was during the second to third
week in June, and in 1987, the fourth. No observations were made in 1988. So far
we have detected no obvious climatic events, such as rainstorms, which trigger
this activity. On several occasions we followed males during their mating
“walkabout” for considerable periods of time. They move rapidly for short
distances, usually only several feet, before they take cover and remain quiet for
varying periods of time. They tend to move down slope, but the movements
otherwise do not seem to be directed. They were most frequently seen in the early
afternoon. Attempts to follow males were unsuccessful and frustrating. They were
easily lost in vegetation and debris, or occasionally remained stationary for very
long periods of time (hours).

Comparisons with other species of Sphodros. — There are similarities and
differences between the webs and behavior of S. niger and those of abboti and
rufipes as noted by Coyle and Shear (1981). The males of abboti behave much as
niger when in search of mates. They are diurnal and seem to rely in part on a
contact pheromone which helps to explain our observations of the behavior of
niger males. In addition niger males both move like and have the appearance of
pompilid wasps or larger, dark gnaphosids. Our single surface web of an adult
female niger , 63 cm in length, was about twice as long as the maximum length of
the aerial webs of adult female abboti and rufipes (35 cm). The number of young,
73 plus for our single female niger is comparable to the average of 79.7 for six
broods of abboti. The surface portion of the niger web is substantially tougher
than the underground portion; the reverse is true of the other two species.

ACKNOWLEDGMENTS

We are grateful to W. A. Shear, F. A. Coyle, and J. A. Coddington for
comments and suggestions on the manuscript. H. Guarisco kindly provided some
needed literature.

THE JOURNAL OF ARACHNOLOGY

LITERATURE CITED

Beatty, J. A. 1986. Web structure and burrow location of Sphodros niger (Hentz). J. Arachnol.,
14:130-132.

Coyle, F. A. and W. A. Shear. 1981. Observations on the natural history of Sphodros abhoti and
Sphodros rufipes (Araneae, Atypidae), with evidence for a contact sex pheromone. J. Arachnol.,
9:317-326.

Gertsch, W. and N. Platnick. 1980. A revision of the American spiders of the family Atypidae
(Araneae, Mygalomorphae). Amer. Mus. Nov. (2704): 1-39.

Morrow, W. 1986. A range extension of the purseweb spider Sphodros rufipes in eastern Kansas
(Araneae, Atypidae). J. Arachnol., 14:119-121.

Manuscript received April 1989, revised June 1989.

Carrel, James E. 1990. Water and hemolymph content in the wolf spider Lycosa ceratiola (Araneae,
Lysoidae). J. ArachnoL, 18:35-40.

WATER AND HEMOLYMPH CONTENT IN THE WOLF SPIDER
LYCOSA CERATIOLA (ARANEAE, LYCOSIDAE)

James E. Carrel

Division of Biological Sciences
University of Missouri-Columbia
Columbia, Missouri 65211 USA

ABSTRACT

Female Lycosa ceratiola, most of whom were gravid when collected in March in Florida, contained
significantly less water than males (2.24 versus 2.88 mg water/ mg dry mass, representing 69 and 74%
of wet mass, respectively). Both sexes had similar amounts of hemolymph in their bodies (32.4% of
wet mass in females and 37.3% in males). The density of hemolymph in male and female spiders at 22-
24° C averaged 1.00 mg/ pi. These results suggest that egg production in female spiders affects their
total water content, most likely because ripening eggs gain energy-rich lipids at the expense of water.
Two commonly used water content indices, which express water mass as a proportion of either wet or
dry body mass, are evaluated.

INTRODUCTION

Water and blood relations in spiders are poorly understood compared to
information concerning insects, mites, and ticks. Moreover, the state of the field
is heterogeneous: many basic physiological problems in spiders have attracted
little attention, whereas a few topics, most notably hemolymph ionic and
biological chemistry, have been well investigated (Pulz 1987; Strazny and Perry
1987; and references therein).

Here I attempt to resolve two apparently contradictory concepts underlying
variability in water content in spiders (Pulz 1987). The first concept is that there
is no consistent difference in water content between the sexes within a species.
The second principle is that individual water content depends in part on lipid
content, which is high in gravid females compared to males. I hypothesized that
water content in gravid females should be significantly less than in males of a
given species. Furthermore I hypothesized that the blood content of spiders might
also show a similar sexual difference.

I here report on experiments with the wolf spider Lycosa ceratiola Gertsch and
Wallace that test these ideas. In addition, I discuss the indices used to express
water content in spiders. To my knowledge this is only the second study of
hemolymph content in a spider. In this study I express water or hemolymph
content as the proportion of spider body mass (Allen 1974).

THE JOURNAL OF ARACHNOLOGY

MATERIALS AND METHODS

Adult male and female L. ceratiola ( N - 148) were collected in March in xeric
scrubby flatwoods at the Archbold Biological Station, Highlands County,
Florida. At this time of year, as indicated by preliminary field surveys,
reproduction is prevalent in this species (J. E. Carrel, unpublished observations).
Spiders were maintained individually in plastic containers as described by Carrel
and Eisner (1984). Their wet mass when alive was measured individually to the
nearest 0.1 mg shortly before being used in tests. Individual spiders were used
only in one test.

Water content of L. ceratiola was determined gravimetrically. Adult spiders
(N = eight of each sex) were weighed, placed individually in a tared vial, killed by
freezing, and then dried to constant mass in an 80° C oven. Water content was
expressed as % wet mass and mg water/ mg dry mass.

To calculate hemolymph content (% wet mass) I determined density and
volume of hemolymph in spiders. Hemolymph density was measured in spiders
( N - eight of each sex) as follows: individuals were anesthetized with carbon
dioxide gas; a leg was amputated at the base; discharged hemolymph (2.7-11.1 jul)
was taken up in a volumetrically calibrated tube previously weighed to 1 ug on a
Cahn 28® electrobalance; the filled tube was reweighed and the volume of fluid in
it was measured. Density of each hemolymph sample was calculated by dividing
its volume by its mass (mg/ /il).

Hemolymph volume in adults ( N - eight of each sex) was determined using the
radiolabeled inulin dilution method (Wharton et al. 1965). Injection (5 jul) was
accomplished with a micrometer syringe into the pericardial region of the
abdomen of a spider anesthetized with carbon dioxide gas. Carboxy- 1 4C-inulin
(sp. act. 2.60 mCi/gram, Sigma Chemical Co.) was dissolved in spider saline
(Rathmayer 1965) to achieve a dosage of 0.1 yuCi per spider. Each spider was
again anesthetized 1 h after injection and hemolymph was collected as previously
described. The hemolymph was discharged immediately from the tube into 1 ml
deionized water in a scintillation vial. Subsequently 15 ml of Aquasol scintillation
fluid was added to each vial and radioactivity was measured in a Hewlett-
Packard Tri-Carb 460C® scintillation counter. In a similar fashion the radio-
activity in aliquots of the inulin stock solution was measured and used as a
reference standard. To correct for counting inefficiencies and quenching effects,
the sample channel ratio (SCR) was used to calculate total radioactivity (cpm) in
each sample. Hemolymph volume of each spider was calculated as follows:

Vb = -LT, — Vi

where: Vb = volume of hemolymph in spider
Vs = volume of hemolymph sample
Vi - volume of solution injected (5 ul)

Q = count of solution injected
Cs = count of hemolymph sample

The reproductive state of female L. ceratiola ( N = 100) was determined in two
ways. Using the method of Riddle (1985), 50 spiders were killed by freezing and
their abdomens were bisected. Specimens with an egg mass greater than one-sixth
of the cross-sectional area of the abdomen were considered gravid. To verify this

CARREL— WATER AND HEMOLYMPH IN LYCOSA

Table 1. — Dry mass and water content in adult Lycosa ceratiola. Differences between values with
the same letter in a column are significant (a = P < 0.001; b = P < 0.01) with Mest. Mean ± SE,
(Range).

Sex

Dry mass mg

Water content

% wet mass

mg water/ mg dry mass

Male

80.1 ± 8.9a

74.0 + 0,9b

2.88 ± 0.1 4b

(48.3 - 117.2)

(71.3 - 78.2)

(2,48 - 3.58)

Female

228.2 + 26.4a

69.0 + l.lb

2.24 + 0.1Qb

(157.5 - 388.4)

(61.5 - 71.2)

(1.59 - 2.47)

procedure, the remaining 50 spiders were inspected at 2=3 day intervals for 4 wk
to ascertain whether each had produced an egg sac.

Statistical analyses of the data were performed manually using the methods
described in Sokal and Rohlf (1987) or by computer using SAS routines (SAS
1985).

RESULTS AND DISCUSSION

Living adult L. ceratiola exhibited a sexual size dimorphism. Data ( X + SE,
N = 24 of each sex) showed female and male spiders weighed 724 ± 56 and 305 ±
29 mg, respectively. This difference, a factor equal approximately to 2.37, was
highly significant (Mest, P < 0.001). Female spiders are larger than males,
presumably because females invest much more in reproduction than males
(Gertsch 1979; Foelix 1982). There was no significant difference (ANOVA, P >
0.01) in wet body mass among spiders used in different experiments.

Female L. ceratiola contained proportionately more dry mass and, therefore,
less water than males (Table 1). By either index used in Table 1, water content in
female spiders was significantly less than in males. The female/ male dry mass
ratio was 2.85, approximately 20% higher than the wet mass ratio.

Whole body water content in L. ceratiola was slightly less than generally
reported for adult spiders from a variety of biomes in North America (Stewart
and Martin 1970; Vollmer and MacMahon 1974; Riddle 1985). In all of these
studies the spiders were well watered in the laboratory, so dehydration should not
be a significant factor. Moreover, Vollmer and MacMahon (1974) found no
correlation between habitat aridity, body mass, and interspecific differences in
water content of spiders. Surely the relationship between water content and
physiological ecology in spiders is sufficiently complex that many more data from
many more species are needed to discern life history patterns.

Density and relative amount of hemolymph was similar in male and female L.
ceratiola (Table 2). Females contained relatively less hemolymph than males, but
because of the variability in the data, the difference between the sexes was not
significant (Mest, P > 0.05). Whether the high degree of intrasexual variablity in
hemolymph content is biologically meaningful or the result of an artifact remains
to be determined.

To my knowledge this is the first report of using dilution of radiolabeled inulin
injected into spiders. Stewart and Martin (1970), using unlabeled inulin as a
blood-born dye, reported the hemolymph in male and female Dugesiella hentzi

THE JOURNAL OF ARACHNOLOGY

Table 2. — Hemolymph density and content in adult L. ceratiola. Differences between values in the
same column are not significant (P> 0.1) with t-test. Mean + SE, (Range).

Sex

Hemolymph density mg/jul

Hemolymph content % wet mass

Male

1.003 ± 0.007

37.3 ± 2.4

(0.97 - 1.03

(28.2 - 46.9)

Female

1.000 ± 0.005

32.4 ± 6.5

(0.98 - 1.02

(26.6 - 41.6)

averages 19.65 and 18.10%, respectively, of wet body mass. Although the
hemolymph content in D. hentzi adults is about one-half as much as in L.
ceratiola , a difference which in part could result from using different
methodologies, nevertheless within each species females tend to have less
hemolymph than males.

A majority (74%) of 50 female L. ceratiola examined internally were found to
be gravid. This method was verified by the finding that a smaller, but
insignificantly different percentage (58%) of 50 females actually produced egg sacs
when maintained for 4 wk in the laboratory (chi-square test, P > 0.05). Hence,
lipid content of female spiders used in these water and blood content studies
presumably was high because most of them contained energy rich eggs. The
energy density of spider eggs, expressed as joules/ g dry mass, generally is 11%
higher than the average for nongravid adult spiders (Anderson 1978).

Water mass (mg)

Figure 1. — Comparison of two indices for water content in a hypothetical spider having dry mass of
1 mg as a function of its absolute water mass. (See text for details). The range of water content values
matches those actually found in various spiders under different conditions, as summarized by Pulz
(1987). For graphical purposes, water content based on wet body mass is shown at one-tenth scale so
that the two lines are similar in scope.

CARREL— WATER AND HEMOLYMPH IN LYCOSA

As indicated in Table 1, the water content of whole spiders can be expressed by
two different indices, one based on the wet mass and the other based on the dry
mass of the animal. Most authors, as cited by Pulz (1987), have used the wet
mass index, often refered to as “percent water”. But is one index scientifically
more robust than the other? One way to answer this question is to examine how
body water content changes as a function of water mass in a spider, under
idealized conditions where dry mass is kept constant (say equal to 1 mg) as if the
animal is undergoing dehydration or rehydration. As shown in Fig. 1, under these
hypothetical conditions the two indices yield two rather different graphs: the wet
mass index levels off asymptotically as the spider gains a lot of water, whereas
the dry mass index rises in a linear fashion across the same range.

From this graphical analysis, clearly the linear dry mass index is preferable to
the curvilinear wet mass index of body water content. An example will illustrate
this conclusion. At high moisture levels, a one percent gain or loss in water
content based on a spider’s wet body mass translates into a large change
approximating 1 mg water/ mg dry mass of the animal.

In conclusion, this study shows that a consistent difference in water content
between the sexes of L. ceratiola can be found when females are gravid. The
presence of eggs evidently increases the lipid and dry mass contents in female
spiders, causing a slight (5%) decline in water content in comparison to male
spiders.

ACKNOWLEDGMENTS

I thank Z. Yang and M. H. McCairel for field and laboratory assistance in
preliminary studies, M. Deyrup and the staff of the Archbold Biological Station
for hospitality and research facilities, J. D. David and G. H. Perrot for technical
assistance, and J. F. Anderson and K. N. Prestwich for reviewing the manuscript.
Supported in part by Research Incentive Funds from the University of Missouri-
Columbia.

LITERATURE CITED

Allen, S. E., ed. 1974. Chemical Analysis of Ecological Materials. Wiley & Sons, New York.

Anderson, J. F. 1978. Energy content of spider eggs. Oecologia, 37:41-57.

Carrel, J. E. and T. Eisner. 1984. Spider sedation induced by defensive chemicals of milliped prey.

Proc. Natl. Acad. Sci. USA, 81:806-810.

Foelix, R. F. 1982. Biology of Spiders. Harvard Univ. Press, Cambridge.

Gertsch, W. J. 1979. American Spiders, 2nd Ed. Van Nostrand Reinhold, New York.

Pulz, R. 1987. Thermal and water relations. Pp. 26-55, In Ecophysiology of Spiders (W. Nentwig, ed.).
Springer- Verlag, Berlin.

Rathmayer, W. 1965. Polyneuronale Innervation bei Spinnen. Naturwissenschaften, 52:114.

Riddle, W. A. 1985. Hemolymph osmoregulation in several myriapods and arachnids. Comp.
Biochem. Physiol., 80A:3 13-323.

SAS. 1985. SAS User’s Guide: Statistics, Version 5 Edition. SAS Institute, Cary, North Carolina.

Sokal, R. R. and F. J. Rohlf. 1987. Introduction to Biostatistics, 2nd Ed. Freeman, New York.

Stewart, D. M. and A. W. Martin. 1970. Blood and fluid balance of the common tarantula, Dugesiella
hentzi. Z. vergl. Physiol., 70:223-246.

Strazny, F. and S. F. Perry. 1987. Respiratory system: structure and function. Pp. 78-94, In
Ecophysiology of Spiders (W. Nentwig, ed.). Springer- Verlag, Berlin.

THE JOURNAL OF ARACHNOLOGY

Vollmer, A. T. and J. A. MacMahon. 1974. Comparative water relations of five species of spiders
from different habitats. Comp. Biochem. Physiol, 47A:753-765.

Wharton, D. R. A., M. L. Wharton, and J. Lola. 1965. Blood volume and water content of the male
American cockroach, Periplaneta americana L - methods and the influence of age and starvation.
J. Ins. Physiol., 11:391-404.

Manuscript received May 1989, revised June 1989.

Tugmon, C. R., J. R. Brown and N. V. Horner. 1990. Karyotypes of seventeen USA spider species
(Araneae, Araneidae, Gnaphosidae, Loxoscelidae, Lycosidae, Oxyopidae, Philodromidae,
Salticidae and Theridiidae). J. Arachnol, 18:41-48.

KARYOTYPES OF SEVENTEEN USA SPIDER SPECIES
(ARANEAE, ARANEIDAE, GNAPHOSIDAE, LOXOSCELIDAE,
LYCOSIDAE, OXYOPIDAE, PHILODROMIDAE,
SALTICIDAE AND THERIDIIDAE)

Cathy R. Tugmon1, Judy D. Brown,
and Norman V. Horner

Department of Biology
Midwestern State University
Wichita Falls, Texas 76308 USA

ABSTRACT

Karyotypes are reported for 17 species from eight families of spiders from Texas and Missouri.
Chromosomal counts (2N) are as follows: Araneidae — Eustala enter tom, 24; Gnaphosidae — Cesonia
sincera, 22 and 24; Nodocion floridanus, 24; Loxoscelidae — Loxosceles reclusa, 18 and 20;
Lycosidae— Lycosa rabida, 28 and 30; Oxyopidae — Oxyopes scalaris, 21; Philodromidae — Tibellus
duttoni, 29; Salticidae— Mae via inclemens, 27 and 28; Marpissa pikei, 28; Metaphidippus galathea, 27
and 28; Peckhamia americana, 22 and 24; Phidippus audax, 28 and 30; Phidippus texanus , 28 and 30;
Platycryptus undatus, 28 and 30; Salticus austinesis, 28 and 30; Tutelina elegans, 27 and 28; and
Theridiidae— Steatoda triangulosa, 22 and 24.

INTRODUCTION

A thorough search of the literature indicates chromosomal data (counts) are
available for approximately 300 of the more than 30,000 spider species (Gowan
1985; Datta and Chatterjee 1988). Most of these are reported from the Old World
and many are identified only at the generic level. This study adds karyotypic data
for 14 additional identified species and three that have been previously reported.

MATERIALS AND METHODS

Specimens for the present study were collected from north-central Texas with
the exception of Oxyopes scalaris Hentz and Tutelina elegans (Hentz) which were
from eastern Missouri.

The meiotic studies were accomplished by examining the ovaries and testes of
penultimate and mature spiders. The meiotic procedure used was an air-dry
method developed by Cokendolpher and Brown (1985). The only modification
was the stain. The commercially available Diff-Quick Solution II was used to
stain the chromosomes. This staining solution consisted of 1.25 g/1 thiazine dye
mixture, 100% PDC (0.625 g/1 azure A and 0.625 g/1 methylene blue) and buffer.

•Present address: Department of Zoology, University of New Hampshire, Durham, NH 03824 USA.

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Five-day-old eggs (embryos) were used for the mitotic studies. The procedure
followed was a modification of Matsumoto’s (1977) method. Substitutions
included the use of methanol instead of ethyl alcohol in the fixative, the use of
four eggs instead of one, and a pH of 7.0 for the saline solution instead of 7.2.
All mitotic preparations were flame dried and stained with Giemsa. The stain was
prepared by mixing 2 to 3 ml of Giemsa with 50 ml phosphate buffer (0.469 g
sodium dihydrogen phosphate, 0.937 g sodium monohydrogen phosphate/ 1
water).

Chromosome numbers were determined by counting spreads for each species.
The most frequent chromosome counts were regarded as the valid number. In
mitotic studies, species where two different consistent counts were noted, they
were assumed to be due to the sex determining mechanism.

Specimens sacrificed for meiotic studies and females that produced the eggs for
the mitotic studies are deposited in the Invertebrate Collection at Midwestern
State University.

RESULTS AND DISCUSSION

Eggs are excellent sources of somatic cells that provide good mitotic spreads.
At present, spider karyotyping techniques for somatic cells are not sufficient to
observe the sex-determining mechanisms. We agree with Matsumoto’s (1977)
deductions that meiotic preparations are necessary for determination of the sexing
mechanisms.

Tables 1 and 2 list the results of meiotic and mitotic works, respectively. The
tables indicate the species studied, diploid (2n) numbers, sex-determining
mechanisms in meiotic studies, and geographic location. References are made to
previous studies where researchers examined the same or closely related species.
Some counts in this study do not agree with the previously reported results (see
Table 1). This may be due to counting error, improper identification or even
geographic variation. Representative photographs of all species examined are
shown in Figs. 1-25 with the exception of Lycosa rabida Walckenaer and
Peckhamia americana (Peckham and Peckham) which were unavailable.

Datta and Chatterjee (1988) report that 55 species of Araneidae have been
karyotyped. The 2n number ranges from 14 to 46 with 24 being the most
common. Our study is the first to report a karyotype for Eustala emertoni
(Banks) (Fig. 1). It is 2n=24, as are 81% of the other Araneidae. Since this is a
mitotic study no sex-determining mechanism is confirmed.

According to the literature 13 different species of Gnaphosidae have been
reported (Painter 1914; Hackman 1948; Suzuki 1952; Mittal 1961). With the
exception of Scotophaeus blackwallii (Thorell), which Mittal (1961) reported as
having 11 autosomal pairs and an XXO-XXXX sex-determining mechanism, all
other Gnaphosidae cytogenetically known have 10 autosomal pairs and an XXO-
XXXX sex-determining mechanism (Painter 1914; Hackman 1948; Suzuki 1952;
Mittal 1961). Cesonia sincera Gertsch and Mulaik (Figs. 2-3) and Nodocion
floridanus (Banks) (Fig. 4) mitotic studies show this same consistency. These two
karyotypes are the first reported for their respective genera.

Our figures show Loxosceles reclusa Gertsch and Mulaik (Loxoscelidae) males
as 2n— 22 and females as 2n=24 and a sex determining mechanism of XXO-

TUGMQN, BROWN & HORNER— SPIDER KARYOTYPES

Table 1. — Meiotic Studies. Species, diploid number, number of individuals examined ( ), sex-
determining mechanism, geographic location and selected supportive references.

Diploid number

Sex determining
mechanism

Geopranhic

Species

Male

Female

Male Female

location

References

ARANEIDAE

Eustala sp.
LOXOSCELIDAE

Loxosceles reclusa

xxo

Asia

Mittal 1961

Gertsch & Mulaik

L. rufipes (Lucas) [prob.

18(9)

20(2)

xxo-xxxx

N.A.

(TX)

Current study

L. laeta- see text]

LYCOSIDAE

xxo-xxxx

S.A.

Diaz & Saez
1966

Lycosa rabida Walck.

28(1)

30(1)

xxo-xxxx

N.A.

(TX)

Current study

L. rabida

OXYOPIDAE

xxo-xxxx

N.A.

(MS)

Wise 1983

Oxyopes seratus (L. Koch)

PHILODROMIDAE

xo-xx

Asia

(Japan)

Suzuki 1952

Tibellus oblongus (Walck.)

xxo-xxxx

Asia

Sokolov 1962

T. tenellus (L. Koch)

SALTICIDAE

Maevia inclemen
[reported as M. vittata

xxo-xxxx

Asia

(Japan)

Suzuki 1952

Hentz]

Peckhamia americana

xxo-xxxx

N.A.

Painter 1914

(Peck. & Peck.)

22(3)

24(3)

xxo-xxxx

N.A.

(TX)

Current study

Phidippus audax (Hentz)

28(1)

30(1)

xxo-xxxx

N.A.

(TX)

Current study

Phidippus audax (Hentz)

Salticus austinensis

xxo-xxxx

N.A.

(TX)

Pinter &
Walters

1971

Gertsch

28(7)

30(3)

xxo-xxxx

N.A.

(TX)

Current study

S. cingulatus (Panzer)
THERIDIIDAE

Steatoda triangulosa

xxo-xxxx

Asia

Sokolov 1960

(Walck.)

22(3)

24(5)

xxo-xxxx

N.A.

(TX)

Current study

S. bipunctata (L.)

xxo-xxxx

Europe

Hackman

1948

XXXX (Figs. 5-6). Of the two Loxosceles species previously reported, the sex-
determining mechanism is identical but they have a different number of
autosomal pairs. Loxosceles rufescens (Dufour) and L. rufipes (Lucus) are
reported by Begak and Begak (1960) and Diaz and Saez (1966) respectively as
2n=20. These workers examined only males. Based upon Gertsch’s (1967) revision

THE JOURNAL OF ARACHNOLOGY

Table 2. — Mitotic Studies. Species, diploid number, number spreads examined ( ) and geographical
location.

Species

Diploid numbers

Geographic location

ARANEIDAE

Eustala emertoni (Banks)

24(4)

N.A.,(TX)

GNAPHOSIDAE

Cesonia sincera Gertsch & Mulaik

22(1)

24(1)

N.A.,(TX)

Nodocion floridanus (Banks)

24(4)

N.A.,(TX)

OXYOPIDAE

Oxyopes scalaris Hentz

21(4)

N.A.,(MO)

PHILODROMIDAE

Tibellus duttoni (Hentz)

29(3)

N.A.,(TX)

SALTICIDAE

Maevia inclemens (Walckenaer)

27(4)

28(4)

N.A.,(TX)

Marpissa pikei (Peckham & Peckham)

28(8)

N.A.,(TX)

Metaphidippus galathea (Walckenaer)

27(8)

28(3)

N.A.,(TX)

Phidippus audax (Hentz)

28(39)

30(12)

N.A.,(TX)

Phidippus texanus Banks

28(3)

30(8)

N.A.,(TX)

Platycryptus undatus (De Geer)

28(3)

30(8)

N.A.,(TX)

Salticus austinensis Gertsch

28(1)

30(1)

N.A. (TX)

Tutelina elegans (Hentz)

27(9)

28(8)

N.A. (MO)

THERIDI1DAE

Steatoda triangulosa (Walckenaer)

22(19)

24(1)

N.A.,(TX)

these reported species, L. rufescens and L. rufipes are probably misidentified and
should be L. gaucho and L. laeta respectively.

Gowan’s (1985) survey of the literature revealed karyotypes of approximately
62 different, identified, species of Lycosidae. Diploid counts range from 22 to 30
with 13 autosomal pairs and an XXO-XXXX sex-determining mechanism being
the most common. Our findings for Lycosa rabida Walckenaer agree with those
of Wise (1983) and match the modal number for the family.

In the Oxyopidae three genera and approximately eight, identified, species have
been karyotyped (Painter 1914; Hackman 1948; Bole-Gowda 1950; Suzuki 1950,
1952; Sharma and Tandon 1957; Mittal 1961). All but Oxyopes salticus L. Koch
(Painter 1914) and Peucetia viridana Stoliczka (Bole-Gowda 1950) have 10
autosomal pairs and an XO-XX sex-determining mechanism. This study revealed
that the mitotic spreads of Oxyopes scalaris (Fig. 7) had a 2n count of 21.

Thirteen autosomal pairs and an XXO-XXXX sex-determining mechanism is
the most common number for members of the Philodromidae (Hackman 1948;
Sokolov 1960; Suzuki 1952). The 2n count obtained from mitotic spreads for
Tibellus duttoni (Hentz) (Fig. 8) is 29. Variation from this count has been
reported for T. oblongus (Walckenaer) (Hackman 1948) and T. tenellus (L. Koch)
(Suzuki 1952) as indicated in Table 1. Further studies are needed for conclusive
counts within the genus and of this species.

Karyotypes from approximately 50 species of Salticidae have been previously
reported by Gowan (1985). Maevia inclemens (Walckenaer) (Figs. 9-10),
previously known as Maevia vittata Hentz, was karyotyped by Painter (1914). He
worked with two morphologically different males but reported no variation in the
chromosome numbers. Only one of the diploid numbers obtained in this study
agreed with Painter.

TUGMON, BROWN & HORNER— SPIDER KARYOTYPES

Figures 1-9. — Chromosome spreads of: 1, Eustala emertoni 2n=24; 2,3, Cesonia sincera\ 2, 2n=22;
3, 2n=24; 4, Nodocion floridanus 2n=24; 5,6, Loxosceles reclusa\ 5, male 2n=18; 6, female 2n— 20; 7,
Oxyopes scalaris 2n=21; 8, Tibellus duttoni 2n=29; 9, Maevia inclemens 2n=27. Scale bar-- 10 /tun.

Karyotypes of Marpissa pikei (Peckham and Peckham) (Fig. 11),
Metaphidippus galathea (Walckenaer) (Figs. 12-13), Peckhamia americana
(Peckham and Peckham), Platycryptus undatus (De Geer) (Figs. 18-19) and
Tutelina elegans (Hentz) (Figs. 21-22) are reported for the first time. As these are

THE JOURNAL OF ARACHNOLOGY

Figures 10-18. — Chromosome spreads of: 10, Maevia inclemens 2n=28; 11, Marpissa pikei 2n=28;
12,13, Metaphidippus galathea; 12, 2n=27; 13, 2n=28; 14,15, Phidippus audax\ 14, males 2n=28; 15,
females 2n=30; 16,17, Phidippus texanus; 16, 2n=28; 17, 2n=30; 18, Platycryptus undatus 2n=28.
Scale bar=10 /um.

also the first reported for each genus no data on related forms are available for
comparison.

Phidippus audax (Hentz) (Figs. 14-15) counts do not agree with those reported
by Pinter and Walters (1971). However, the meiotic and mitotic counts in this

TUGMON, BROWN & HORNER— SPIDER KARYOTYPES

Figures 19-24. — Chromosome spreads of: 19, Platycryptus undatus 2n=30; 20, Salticus austinesis
male n=13 and XXO (the X’s are indicated with arrows); 21,22, Tutelina elegans; 21, 2n=27; 22,
2n=28; 23,24, Steatoda triangulosa", 23, males 2n=22; 24, females 2n=24. Scale bar=10 /im.

research were consistent and supportive for 2n counts of 28 and 30 with a sexing
mechanism of XXO-XXXX. These diploid numbers were also found by
Maddison (Gowan 1985). Phidippus texanus Banks (Figs. 16-17) diploid counts
from mitotic studies were consistent with those of P. audax. Salticus austinesis
Gertsch (Fig. 20) diploid counts agree with Salticus cingulatus (Panzer) (Sokolov
1960) and Salticus scenicus (Clerck) (Hackman 1948). Phidippus texanus Banks
and Salticus austinesis Gertsch are reported for the first time.

Eight genera and 13 species of Theridiidae have been karyotyped. With the
exception of Chrysso venusta (Yaginuma) which has 11 autosomal pairs and an
XXO-XXXX sex-determining mechanism (Kageyama and Seto 1979) all reported
theridiids have 10 autosomal pairs and a XXO-XXXX sex-determining
mechanism. Steatoda triangulosa (Walckenaer) (Figs. 23-24) typifies this pattern.

Many additional species must be karyotyped, and correct identification
determined before assessing any inter- and intra-specific chromosomal variation.
With the development of consistent banding techniques in spiders, it may be
possible to determine homologies and devise a standard numbering system at
least within some genera. It could then be possible to determine the diploid
number for each sex from somatic cells such as eggs (embryos).

THE JOURNAL OF ARACHNOLOGY

ACKNOWLEDGMENTS

We want to thank the Biology Department of Midwestern State University for
providing the funds, facilities and equipment for this research. This paper is the
combined results of separate theses submitted by Tugmon and Brown for their
masters degrees. Appreciation is expressed to Jane Lindsey who typed the
manuscript. We especially thank James Cokendolpher, Bruce Cutler, Elsa
Galbraith, Jon Reiskind and Fred Stangl, Jr. for their reviews and constructive
suggestions to improve the paper.

LITERATURE CITED

Bole-Gowda, B. N. 1950. The chromosome study in the spermatogenesis of two lynx-spiders
(Oxyopidae). Proc. Zool. Soc. Bengal., 3:95-107.

Begak, W., and M. L. Begak. 1960. Constituicao cromossomica de duas especies de aranhas do genero
Loxosceles. Rev. Brasileira Biol., 20:425-427.

Cokendolpher, J. and J. Brown. 1985. Air-dry method for studying chromosomes of insects and
arachnids. Entomol. News, 96:114-118.

Datta, S. N. and K. Chatterjee. 1988. Chromosomes and sex determination in 13 araneid spiders of
North-Eastern India. Genetica, 76:91-99.

Diaz, M. O. and F. A. Saez. 1966. Karyotypes of South-American Araneida. Mems. Inst. Butantan,
33:153-154.

Gertsch, W. J. 1967. The spider genus Loxosceles in South America (Araneae, Scytodidae). Bull.
American Mus. Nat. Hist., 136:117-174.

Gowan, T. D. 1985. The life history and reproduction of the wolf spider Lycosa lentia Hentz.

Gainesville: University of Florida. 259 pp. Dissertation.

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gechlechtschromosomen. Acta. Zool. Fennica, 54:1-101.

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Matsumoto, S. 1977. An observation of somatic chromosomes from spider embryo-cells. Acta.
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Manuscript received January 1989, revised June 1989.

Fernandez-Montraveta, C. y J. Ortega. 1990. El comportamiento agonistico de hembras adultas de
Lycosa tarentula fasciiventris (Araneae, Lycosidae). J. Arachnol., 18:49-58.

EL COMPORTAMIENTO AGONISTICO DE HEMBRAS
ADULTAS DE LYCOSA TARENTULA FASCIIVENTRIS
(ARANEAE, LYCOSIDAE)

Carmen Fernandez-Montraveta y Joaquin Ortega

Dpto. Psicologia Biologica y de la Salud
Universidad Autonoma
Cantoblanco, 28049-Madrid Espana

ABSTRACT

Dyadic interactions between adult females of Lycosa tarentula fasciiventris in the laboratory are
described. Our results show motor patterns that are not very specific to the context, little ritualized
fighting, resulting in a high frequency of cannibalism and a great variability in the duration of the
sequences.

RESUMEN

Se describen las interacciones diadicas entre hembras adultas de Lycosa tarentula fasciiventris en el
laboratorio. Nuestros resultados muestran la existencia de patrones motores poco exclusivos del
contexto y bajo nivel de ritualizacion en la lucha, que se refleja en un indice de canibalismo elevado,
asi como una gran variabilidad en la duracion de las secuencias.

INTRODUCCION

El estudio del comportamiento agonistico en las aranas, y en general en todas
las especies animates, se ha centrado, fundamentalmente, en las interacciones
entre machos adultos (Dijkstra 1969, 1978; Aspey 1976, 1977; Jackson 1982;
Halliday 1986). El interes por estos sujetos para tales estudios ha derivado de la
funcion que se adjudica al comportamiento agonistico como tecnica de
competicion intraespecifica por recursos limitados (Wilson 1975).

En el caso de las aranas las hembras presentan, en general, un repertorio
comportamental menos complejo que el de los machos no mostrando, por
ejemplo, un cortejo activo. Son los machos los que realizan la busqueda de las
hembras, exhibiendo en este contexto una mayor frecuencia de encuentros
agonisticos entre ellos, en los que las hembras han sido comunmente consideradas
el recurso por el que compiten (Vollrath 1980; Jackson 1982). Por esta razon se
han planteado, con relativa frecuencia, estudios sobre competicion, relaciones
jerarquicas o relaciones territoriales entre machos adultos (Aspey 1977; Dijkstra
1978; Goist 1982; Austad 1983). Con menor frecuencia, estas mismas cuestiones
han sido planteadas con respecto a las hembras adultas (Riechert 1978, 1986;
Nossek & Rovner 1984; Hodge 1987). Sin embargo estas podrian ser, en algunos
casos, los sujetos idoneos para el analisis de estos problemas.

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En muchas especies de Lycosidos, los machos no se alimentan tras alcanzar la
madurez sexual, pierden la vinculacion con un area concreta y vagan en busca de
hembras adultas. En Lycosa tarentula fasciiventris Dufour, las hembras, por el
contrario, suelen permanecer en el nido, donde se alimentan y aparean. Si se
admite que el comportamiento agonistico es una tecnica de competicion por
recursos limitados, las hembras podrian ser un buen modelo para su estudio en
esta especie, siendo el recurso la ocupacion de un nido o de una localizacion
privilegiada para la obtencion de alimento (Riechert 1978, 1982).

Nos hemos propuesto analizar el comportamiento exhibido por hembras
adultas de L. tarentula fasciiventris en interacciones diadicas compitiendo por un
nido. En este trabajo presentamos una description de la forma en que se
desarrolla este comportamiento en dicho contexto, su resultado y sus
consecuencias.

MATERIAL Y METODOS

Se han utilizado 40 hembras adultas, recogidas del campo como formas
inmaduras, en su antepenultima fase de desarrollo, en las primaveras de 1984 y
1986. Todos los ejemplares procedian de la zona que rodea a la Universidad
Autonoma de Madrid. Desde su captura, fueron mantenidas en el laboratorio en
condiciones de humedad, temperatura y alimentation constantes, con domination
artificial y fotoperiodo de 10 horas de luz y 14 de oscuridad, hasta su observacion
durante los meses de marzo, abril y mayo de 1985 y 1987, respectivamente.
Durante este periodo, permanecieron en terrarios individuales con aislamiento
visual del exterior, realizandose registros periodicos del peso y de la respuesta a
las presas, asi como medidas del tamano corporal en cada una de las mudas que
sufrieron los animales. A1 alcanzar la fase adulta, los individuos fueron medidos;
se utilizo como criterio de su tamano el product© de la longitud por la anchura
del prosoma (Aspey 1977).

Las observaciones se realizaron en terrarios de 30x15x15 cm, con paredes lisas
y opacas y sustrato de tierra. El nido se construyo artificialmente adosado a la
pared anterior, de forma que su interior pudiera ser visible durante los periodos
de observacion; fuera de estos periodos, permanecio aislado visualmente del
exterior.

Las aranas se observaron por parejas formadas al azar en base a una tabla de
numeros aleatorios, de tal manera que una de las dos era colocada en el terrario
ocupado por la otra. El criterio de cual de los dos miembros de la pareja era la
residente fue tambien por azar, y se utilizaron solo aquellas hembras residentes
que habian pasado al menos 7 dias en el terrario, ocupando normalmente el nido
y comiendo alii.

Las observaciones tuvieron una duration minima de 30 minutos, y hasta el
final de la interaccion en el caso de que esta se produjera. El criterio de inicio y
finalizacion de la interaccion fue espacial. Se consider© que una interaccion se
iniciaba cuando la distancia que separaba a ambos animales era igual o inferior a
6 cm, existiendo orientation por parte de alguno de ellos hacia el otro, si las
aranas se encontraban fuera del nido. Si la interaccion se producia en el interior
del nido, a partir del momento en que la intrusa apoyaba el primer par de patas
en el. El criterio de finalizacion de la interaccion fue el alejamiento a mas de 6 cm

FERNANDEZ Y ORTEGA— COMPORTAMIENTO AGONISTICO EN HEMBRAS

y perdida de orientacion por parte de una de las dos hembras, sin que existiera
nueva orientacion durante los 5 minutos siguientes.

Desde el inicio hasta el final de la observacion, se registraron en cinta de video,
fotografia seriada y por escrito todas las actividades y movimientos realizados
por los animales, transcribiendose posteriormente los datos. La intrusa era
retirada tras el registro, no observandose un animal mas de una vez en el mismo
dia.

De la observacion de 73 parejas distintas, se obtuvieron un total de 33
secuencias de interaccion. A partir de los datos obtenidos, se ban descrito los
patrones motores utilizados, el desarrollo y el resultado de las interacciones. Para
cada interaccion, se ha medido su duracion en segundos, calculandose el valor
medio, desviacion standard y coeficiente de variation medido por:

C.V. - SD x 100/x

Como variables independientes, se han controlado el tamano de las dos
hembras, su diferencia y la situation de residencia previa en la interaccion. Para
medir la dependencia entre el resultado y las variables individuals se ha utilizado
una prueba de Chi cuadrado. En el caso de la variable “duracion”, se ha
calculado el coeficiente de correlation, dado por:

r = sXy/Sx Sy, siendo Sxy la covarianza entre x e y, y Sx, Sy las desviaciones
standard de x e y, respectivamente.

RESULTADOS

Cuando se introduce a la hembra intrusa, se observa un periodo inicial de
“adaptation” de alrededor de cinco minutos, durante el cual el animal que ha
sido trasladado permanece inmovil. Cuando inicia el movimiento, su
comportamiento consiste en desplazamientos rapidos y erraticos por el terrario,
con el cuerpo en posicion erguida y proximo a las paredes, que intenta
ocasionalmente escalar. No se observa direccionalidad aparente en estos
desplazamientos.

En el curso de estos desplazamientos las hembras exhiben un movimiento de
“sondeo” de palpos, y de “golpear con el primer par de patas”. Tanto uno como
otro movimientos no van acompanados de cambios en la direction del
desplazamiento con respecto a la posicion del nido.

La localization de este parece producirse por azar. Una vez en contacto con el
brocal, la hembra realiza movimientos de palpos y del primer par similares a los
mencionados anteriormente (Fig. 1), introduciendose lentamente en el nido. Esta
introduction se realiza con el primer par de patas extendido y con movimientos
de los palpos sobre las paredes del nido (Fig. 2). Este patron de comportamiento
se ha observado en la introduccion a cualquier nido, tanto si estaba ocupado
como si no.

La residente suele permanecer inmovil en el interior del nido ante el
desplazamiento de la intrusa. En los casos en los que, por alguna razon, no lo
ocupa o se encuentra sobre el brocal en el momento de iniciarse la observacion,
puede orientarse ante el movimiento de la otra arana a una distancia de hasta 25

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Figura 1. — Sondeo de palpos de la hembra intrusa sobre el brocal. Se observa como la hembra
pliega los palpos sobre un hilo de seda del brocal de un nido.

Figura 2. — Introduction de la hembra intrusa en el nido. Se observa el primer par de patas
extendido y los palpos plegados sobre el brocal.

FERNANDEZ Y ORTEGA— COMPORTAMIENTO AGONISTICO EN HEMBRAS

Tabla 1. — Tipos de interacciones agonisticas entre hembras. R = secuencias breves, en las que la
interaccion se resuelve rapidamente; L = secuencias largas, de resolution lenta.

Ocurreecia

N. inter.

Secuencias

R L

Capturas

Dentro nido

Fuera nido

Total

cm, sea cual sea la position relativa de ambas. En la Tabla 1 aparece reflejada la
frecuencia con la que se han observado interacciones fuera y dentro del nido.

Cuando se encuentra en el nido, la hembra residente no se orienta hasta que la
intrusa realiza movimientos sobre el brocal o se introduce en el. Esta
introduction se realiza lentamente, y la orientation no suele producirse hasta que
la distancia entre ambas se ha reducido a 3-5 cm. El comportamiento de la
residente consiste en dar un salto hacia adelante en direction a la intrusa con el
primer par de patas extendido y elevado y los queliceros abiertos, most rand o una
pauta que hemos llamado “abalanzarse”.

Tras la embestida, algunas interacciones se resuelven rapidamente. En estos
casos, a la embestida de la residente y tras el contacto frontal con el primer par
de patas, puede seguir la huida de la intrusa o, en algunos casos, su captura. En
otras ocasiones, la intrusa responde elevando a su vez el primer par de patas y
abriendo queliceros (Fig. 3). Se puede llegar a observar, en estos casos, un
contacto de todas las patas (“traba”) similar al que se observa en la captura y

Figura 3. — Exhibicion de queliceros abiertos. En la parte superior se observa a la hembra intrusa
con el primer par extendido y los queliceros abiertos. En la parte inferior, se observa una exhibicion
de amenaza de la hembra residente.

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sujecion de presas de gran tamano, mostrando ambas arafias los quell cer os
abiertos y repetidos intentos de morder a la adversaria. El resultado de la traba
puede ser, de nuevo, la huida de una de las dos aranas o, en algunos casos,
finalizar con la captura de una por parte de la otra (Tabla 1).

Tambien puede, tras este primer contacto, producirse un retroceso por parte de
la intrusa, aun permaneciendo en el interior del nido o sobre el brocal, con
sucesivos intentos de aproximacion. En estos casos en que la interaccion no se
resuelve rapidamente, el enfrentamiento se puede mantener hasta mas de 8 horas,
sucediendose aproximaciones de la intrusa con el primer par de patas extendido
hacia adelante, posiciones de inmovilidad con el primer par extendido y los
queliceros abiertos y “tamborileo de los palpos” En el interior del nido, la
hembra residente suele permanecer inmovil, manteniendo la posicion de primer
par extendido y elevado hasta la vertical y queliceros abiertos (“amenaza”). Es de
destacar que, en algunas ocasiones, se ha observado que en los mementos en que
la hembra residente abandona esta posicion, pierda o no la orientacion hacia la
adversaria, esta intenta la introduction en el nido. En algunos casos, la distancia
entre las dos hembras en este tipo de interaccion es tan pequena que se observa
contacto directo y mantenido entre los queliceros de ambas.

En estos casos la interaccion se resuelve, tambien, tras un ataque, con la huida
de una de las dos hembras o su captura (Tabla 1) permaneciendo la otra en el
interior del nido; consideramos a esta ultima la vencedora en la interaccion. Tan
solo en un caso se observe que las dos aranas se separaran quedando ambas en el
interior del nido, una de ellas en el fondo y la otra sobre el brocal, no orientadas
una a la otra. La hembra vencedora puede, incluso, perseguir a la otra hasta una
distancia de dos o tres cm del brocal, manteniendo la orientacion y la posicion de
amenaza hasta varios minutos.

Cuando las interacciones ocurren fuera del nido (Tabla 1), la aproximacion de
la residente a la intrusa se produce de forma escalonada, “a saltos”, con xel
cuerpo en posicion erguida y un avance casi simultaneo de las patas delanteras,
en desplazamientos cortos, rapidos y en linea recta que recuerdan la
aproximacion a grandes distancias a presas de gran tamano.

Cuando la distancia entre ambas se reduce a 3-5 cm, se puede producir la
orientacion de la hembra intrusa. Una vez ocurrida, el enfrentamiento entre
ambas es frontal, desarrollandose la interaccion en la forma descrita
anteriormente en el interior del nido: suele resolverse tras el contacto y, en
ocasiones, la traba, huyendo una de las dos aranas y permaneciendo inmovil la
otra, que mantiene durante algunos minutos la posicion y la orientacion. En otros
casos, se observan sucesivas aproximaciones por parte de esta ultima,
produciendose repetidos contactos y huidas de la primera (Tabla 1).

En algunos casos, no hay orientacion por parte de la hembra intrusa; puede
huir, sin que haya contacto, ante la aproximacion de la residente, o bien resultar
capturada tras una embestida a corta distancia.

La comparacion de las frecuencias de las secuencias R y L (Tabla 1) cuando la
interaccion tiene lugar dentro y fuera del nido da un x = 1.30 (x2 0.05,1 = 3.84);
la comparacion de las frecuencias de captura en ambos contextos da un x2 —
LOO.

La captura ha sido el resultado final de 8 de las 33 interacciones observadas.
En 5 de estos casos, se produjo tras una interaccion frontal larga, y en los otros
tres tras aproximacion lateral o posterior. En todos los casos, el resultado de la

FERNANDEZ Y ORTEGA— COMPORTAMIENTO AGQNISTICO EN HEMBRAS

Tabla 2. — Resultado de las interacciones en funcion de la residencia previa y del tamano. VR =
vence individuo residente; VI = vence individuo intruso; VM = vence individuo mayor; Vm = vence
individuo me nor.

Variable

Resultado

Residencia

Tamano

captura fue la ingestion total de la congenere. Se observaron, ademas, cuatro
intentos de captura en interacciones frontales que resultaron en la mordedura de
alguna region no vital (patas) y la posterior separation de las aranas sin resultado
final de muerte. En los otros 25 casos, el resultado final de la interaccion
consistio en la huida de una de las dos aranas.

En la Tabla 2 se indica cual de las dos aranas resulto vencedora en funcion de
las variables “residencia” y “tamano”. A1 aplicar una prueba de Chi cuadrado a
los resultados de esta Tabla se obtiene que difieren del azar, tanto con respecto a
la residencia x ~ 6.82, p <0.05), como al tamano (x2 = 5.12,/? <0.05).

En la Tabla 3 se presenta el resultado de las interacciones en funcion del
tamano de la residente. No existe dependencia significativa entre ambas variables
X2 = 3.82), aunque el valor obtenido esta muy proximo al valor significativo (x2
= 3.84, p <0.05). Sin embargo, las aranas de mayor tamano tienden a ganar mas
luchas cuando son residentes (x2 = 5.26,/? <0.05).

La duracion de las interacciones observadas es muy variable. El valor medio de
la duracion es de 2509.55 segundos, y su desviacion standard 5254.16. Se ha
calculado el coeficiente de correlation entre las variables “duracion de la
interaccion” y “diferencia de tamano” para el grupo en que el animal residente es
el de mayor tamano ( r = —0.36) y el grupo en que el residente es el animal de
menor tamano (r = —0.32). Ninguno de estos valores es significativo
estadisticamente (p <0.05).

DISCUSION

El comportamiento exhibido por hembras adultas de L. tarentula fasciiventris
en interacciones diadicas es similar al descrito por Nossek & Rovner (1984) en
otras especies del genero. La estrategia general, asi como los patrones motores del

Table 3. — Resultado de las interacciones en funcion de las dos variables individuales.

Tamano residente

Resultado

VR VI

Total

Mayor

Menor

Total

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comportamiento, no difieren tampoco, de forma significativa, de los descritos
para los animales de este sexo y fase de desarrollo en otros contextos (Ortega
1985; Ortega et al. 1986). El nivel de especificidad de los patrones motores
exhibidos es, por lo tanto, bajo, y menor que el observado en interacciones
diadicas entre machos adultos en esta especie (Ortega et al. 1984).

El nivel de intensificacion de las luchas es mayor que el observado, tanto en
encuentros entre machos adultos de esta especie (Ortega et al. 1984), como en los
descritos en otras especies (Nossek & Rovner 1984). Este hecho se traduce en el
elevado indice de cahibalismo observado.

La mayor parte de las interacciones se han registrado en el interior de los
nidos, y su resultado consiste en el abandon© de este por parte de una de las dos
hembras. Este hecho nos lleva a postular que estas interacciones pueden
interpretarse como competitivas, siendo el recurso en litigio la ocupacion de un
nido. Dado el abrigo y la proteccion a temperaturas extremas que proporcionan
(Humphreys 1987), puede tratarse de un recurso importante para la supervivencia
de los individuos.

El elevado valor de este recurso podria explicar el alto nivel de intensificacion
que se observa en los encuentros estudiados. Se ha postulado, de hecho, que la
intensificacion de los encuentros se puede producir si el valor del recurso es muy
alto (Maynard Smith & Parker 1976; Riechert 1982; Huntingford & Turner
1987).

No hemos detectado diferencias en la frecuencia de interacciones breves y
largas o de capturas en funcion de que el encuentro se produzca o no en el
interior del nido. En otros estudios no se ha detectado, tampoco, correlacion
entre la intensidad de la lucha y el valor del recurso (Hodge 1987).

El elevado riesgo de lesion como consecuencia de la intensificacion podria
haber llevado al desarrollo de estrategias de comportamiento que minimizaran los
riesgos a los adversaries del tipo de “si eres residente ataca, y si eres intrusa
huye” (Maynard Smith 1974; Hammerstein 1981). Esta hipotesis permitiria
explicar la predictibilidad del resultado con respecto a la residencia que hemos
observado. Sin embargo, no todas las interacciones se resuelven rapidamente en
favor del individuo residente.

La existencia de contacto fisico en la mayor parte de las interacciones podria
indicar que la resolucion de estos conflictos se produciria, basicamente, tras la
evaluation de parametros fisicos del adversario (Turner & Huntingford 1986).
Nuestros resultados concuerdan con la hipotesis de que el animal de mayores
fuerza o tamano tiene mas probabilidades de resultar vencedor en estos
encuentros (Aspey 1977; Riechert 1986).

La interaccion de las dos variables de asimetria no queda clara a partir de los
resultados obtenidos, aunque se observa una tendencia a que la probabilidad de
veneer de la hembra residente sea mayor cuando es la de mayor tamano. La
variabilidad de las secuencias podria reflejar las diferentes situaciones en que se
puede encontrar un animal en funcion del tamano y residencia relatives,
respondiendo las secuencias lentas a situaciones en las que las probabilidades de
veneer de la intrusa, en funcion de su tamano, fueran grandes, y las secuencias
rapidas a los casos en que no fuera asi. Estos planteamientos se ajustan a la
tendencia a una correlacion negativa que hemos observado entre las variables
“diferencia de tamano” y “duration de la interaccion”: las interacciones mas

FERNANDEZ Y ORTEGA - COMPORTAMIENTO AGONISTICO EN HEMBRAS

largas corresponden a las situaciones en las que la diferencia de tamario es
pequena.

Estos resultados concuerdan con la suposicion de que los animales utilizan las
interacciones para obtener informacion acerca de su tarnano relativo. Planteamos
que la interpretacion funcional de los patrones motores exhibidos en este
contexto no deberia tanto suponer que son senales que informan de la especie y
sexo del animal, permitiendo el reconocimiento intraespecifico y disminuyendo el
riesgo de que se produzca una respuesta predadora indiscriminada (Krafft 1982),
como que son patrones que servirian a los individuos para evaluar la situacion a
la que se enfrentan.

AGRADECIMIENTOS

Agradecemos a William Eberhard y a Carlos E. Valerio su revision y
sugerencias a este manuscrito. A Jose Maria Calpena, le agradecemos la
elaboracion del material fotografico.

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fasciiventris Dufour (Araneae: Lycosidae). Biol. Behav., 10: 55-65.

THE JOURNAL OF ARACHNOLOGY

Ortega, J., C. Fernandez y E. Pablos. 1984. Un ethogramme ouvert du comportement agonistique des
males adultes chez Lycosa fasdiventris Dufour (Araneae, Lycosidae). Pp. 309-312. Col. Int. d*
Ethologie. SFECA, Barcelona.

Ortega, J., C. Fernandez y E. Pablos. 1986. Comportamiente sexual en Lycosa torentuiu fasdiventris
Dufour (Araneae, Lycosidae). Una aproximacion initial Act. X Congr. Int. Arachnol Jaca /
Espafia, 1:103-106.

Parker, G. A. and D. I. Rubenstein. 1981. Role assessment, reserve strategy and acquisition of
information in asymmetric animal conflicts. Anim. Behav., 29:221-240.

Riechert, S. E. 1978. Energy-based territoriality in populations of the desert spider Agelenopsis aperta
(Gertsch). Symp. ZooL Soc. London, 42:211-222.

Riechert, S. E. 1982. Spider interactions strategies: communication vs. coertion. Pp. 281-316, In
Spider Communication: Mechanisms and Ecological Significance. (P. N. Whitt & J. S. Rovner).
Princeton Univ. Press, Princeton.

Riechert, S. E. 1986. Spider fights as a test of evolutionary games theory. Amer. Scien., 74:604-610.

Turner, A. and F. Huntingford. 1986. A problem for game theory analysis: assessment and intention
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Vollrath, F., 1980. Male body size and fitness in the web-building spider Nephila clavipes. Z.
Tierpsychol., 53:61-78.

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Manuscript received May 1988, revised June 1989.

Cohn, J. 1990. Is it the size that counts? Palp morphology, sperm storage, and egg hatching frequency
in Nephila clavipes (Araneae, Araneidae). J. Arachnoh, 18:59-71.

IS IT THE SIZE THAT COUNTS? PALP MORPHOLOGY,
SPERM STORAGE, AND EGG HATCHING FREQUENCY
IN NEPHILA CLAVIPES (ARANEAE, ARANEIDAE)

Jeffrey Cohn1

Department of Psychology, Tulane University
New Orleans, Louisiana 70118 USA

ABSTRACT

This study investigated the relationship between male size and reproductive success in Nephila
clavipes , a neotropical orb-weaving spider. Gross and palpal size variation were examined in relation
to copulatory behavior, sperm transfer/uptake, and utilization by the female. The effect of conductor
breakage was also evaluated by assessing the timing of its occurrence and its influence on sperm
transfer.

There was less variation in palp size of male N. clavipes than in other aspects of male morphology.
Gross male body size correlated most highly with how much sperm was produced, transferred to, and
stored by the female. Size of the male was not related, however, to the percentage of sperm actually
transferred. The number of sperm retained by the female was influenced by the time of mating, but
not by copulatory behavior. Approximately twice as many sperm were found in the palps of virgin
males as were found in combined totals from mated pairs. This suggests that a substantial percentage
of sperm transferred by the male is not stored by the female. None of the variables analyzed in this
study greatly influenced the percentage of eggs eventually hatching. Conductor breakage seriously
interfered with sperm transfer but occurred less often than expected and did not appear to result from
copulatory activity.

INTRODUCTION

Individual differences in invertebrate male morphology may influence
copulatory behavior (Jackson 1980; Thornhill and Alcock 1983; Christenson
1984). Male morphological variation may differentially affect internal processes in
the female as well. Eberhard (1985) postulated that females in a wide variety of
taxa may copulate with many males but discriminate based upon characteristics
of the males’ genitalia, fertilizing her eggs with sperm from the most desirable
male. This might be accomplished through control of intromission, and
differential uptake of sperm, among other mechanisms (Eberhard 1985). Once
copulation has begun, females could monitor such variables as intensity or quality
of stimuli received, thereby affecting the timing and consequences of copulation
including uptake and storage (Jackson 1980; Thornhill and Alcock 1983;
Eberhard 1985, 1986).

‘Present address. Environmental Health Sciences Center, P.O. BOX EHSC, University of Rochester,
School of Medicine and Dentistry, Rochester, NY 14642. This work was part of a doctoral
dissertation completed in partial fulfillment of the requirements for the Ph.D. at Tulane University in
1988.

THE JOURNAL OF ARACHNOLOGY

The genitalia of male golden orb-weaving spiders (Nephila clavipes L.) are not
noted for great complexity (Schult and Sellenschlo 1983). One outstanding
characteristic, however, is the size of the conductor. Males of similar weight and /
or body length, differing in conductor size, will almost certainly differ in the
stimulation they provide the female, possibly affecting how much sperm is stored
and later utilized by the female. Selective pressures determining conductor size
could be open-ended, i.e., continuous pressure for ever larger (or smaller) size, or
restrictive, i.e., males with an optimal genitalic size having an advantage over
males with larger or smaller conductors. In this study, variation in N. clavipes
palpal morphology was first assessed and compared to variation in more gross
aspects of male size and sperm production. The relationships of natural and
experimentally induced palp variation with transfer/ storage, copulatory behavior,
and egg hatching percentage were then evaluated. Because reproductive behavior
of N. clavipes differs depending upon the age of the female (Christenson et al.
1985), palpal variation could have different effects on the uptake of sperm by
young and mature adult females. Males were therefore mated with females either
immediately following the final molt or two weeks post-molt.

METHODS

Study site — The study was conducted at the F. Edward Hebert Center of
Tulaee University, approximately 20 km south of New Orleans in Belle Chasse,
La. The facility is situated on 500 acres of hardwood, bottomland forest of elm,
maple, oak, hackberry, and box elder. The site is transected by dirt roads,
drainage ditches, and a series of lagoons.

Subject selection. — One hundred sixty-seven male and 157 female 1 V. clavipes
were collected at either the Hebert Center or the Barataria unit of Jean Lafitte
National Historical Park in Barataria, La., in July and August 1987. Males were
selected based upon coloration, web structure, and the presence of sperm webs,
thus ensuring all were approximately the same age, that is, within one or two
days after their final molt (Myers and Christenson 1988). Seventeen males, to be
included in the virgin male analysis, were selected for very small size (less than 6
mm cephalothorax-abdomen length) or very large body size (greater than 9 mm).
Those to be included in the two mated male studies were not selected for size.
Females selected were between 18-20 mm in cephalothorax-abdomen length. This
ensured that they were in their penultimate instar (Moore 1977), The spiders were
housed in 123 X 62 X 62 cm boxes constructed of wood furring strips sided with
Fiberglas© screening. Female subjects were presented one or two mealworm
larvae each day.

Female N. clavipes were divided into four groups. The first variable was the
female’s age at mating: Day of final molt (Day 0) or two weeks post-molt (Day
14). The second variable, was the measure of reproductive success: Number of
sperm found in female’s sperm storage sacs (Sperm) or percent of clutch hatched
(Egg). This resulted in a 2 X 2 (age vs measure) factorial design.

Initial palp evaluation. — In daily groups of approximately 20, 100 male subjects
were brought into the lab before assignment to females. Males were subjected to
hypothermia by placing them in a refrigerator for a few minutes and then
checked for the occurrence of conductor breakage. Those found to have broken

COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES

conductor tips were excluded {N = 4). Males were not kept out of the field for
more than 24 hours.

Mating procedure. — Males in the Day 0 groups were housed together until a
female’s web showed signs of degeneration, indicating a molt was to occur within
a few days. At this time a male was randomly selected from the storage box
(similar to female boxes) and placed via a stick near the hub position above the
female. Among Day 14 dyads, virgin females were supplied with males 14 days
after their final molt. After placing the male, a mealworm was added to the web
to facilitate female receptivity (Christenson et al. 1985). Males in both conditions
were rarely housed apart from females for more than two days.

Behavioral records. — Serial recording was conducted for a minimum of one
hour on the day of the female’s final molt in Day 0 females and following prey
capture or the onset of copulation in Day 14 females (whichever occurred first).
Specific behaviors recorded included amount of time spent in copula (min per h),
the number of copulatory bouts (BOUT - the number of observed palpal
insertions of at least 5 sec duration), rates of hematodochal bulb contractions
(BC - mean rate per min), number of palp pounding bouts (PP - male rapidly
drums his palps on epigynum of the female, 1 sec separating bouts), and number
of female fends (FF). The latter was defined as any female behavior which either
immediately terminated a copulatory bout or immediately caused a male to move
off of or away from her venter. Fends generally included a brisk brushing of the
male with the female’s third pair of legs.

Subsequent analyses of male size. — Males were sacrificed by hypothermia. Wet
weights were taken and measurements of cephalothorax-abdomen length (CthA)
and tibia-patella length (TiPt) were made. Conductors were rechecked to
determine frequency of breakage in non-virgin males. Palps were then removed. If
not broken, the right palp was measured on a Quantimet 970 Image Analyzer®,
otherwise the left palp was used. Four separate measures of palpal length were
made (Fig. 1): 1. overall palp length along its retrolateral axis (PLRA); 2. length
of conductor along its prolateral axis (CLPA); 3. length of conductor along
prolateral axis below the conductor buttress (CLBB); 4. width of conductor at
widest point (CndW). Gross and palpal measurements were taken twice on 10
males. Correlations between first and second measurements were greater than or
equal to 0.98.

Some slight differences in morphology were found between males assigned to
Day 0 and Day 14 females. As males were randomly assigned to these groups,
and since both groups were run in equal numbers throughout the summer, these
differences were likely due to chance. There were trends toward significantly
larger tibia-patella length (FI, 135 = 3.20; p = .076) and greater weight in Day 0
males (FI, 135 = 3.88; p = .051). There was a tendency for Day 0 males to have
larger conductors in three of four measures: PLRA (FI, 135 = 2.98; p = 0.086),
CLPA (FI, 135 - 3.52; p = 0.063), CLBB (FI, 135 = 0.00; p = 0.973), CndW
(FI, 135 = 4.03; p = 0.047).

Conductor manipulation. — To determine the effects of conductor breakage on
copulatory behavior and sperm transfer/ storage, conductor tips of 10 males were
severed with a scalpel blade. The cuts were made approximately 0.2 mm from the
distal end of the conductor, about the length which is occasionally broken off in
nature. Males were maintained outdoors in separate boxes for two days after this
procedure to await placement on a female’s unrepaired web. Ten additional males

THE JOURNAL OF ARACHNOLOGY

Figure 1. — Measurements of palp morphology. Retrolateral view on the left, prolateral on the right.
1 = PLRA - Palp length retrolateral axis, 2 = CLPA - Conductor length prolateral axis, 3 =
Conductor length below buttress, 4 = CndW - conductor width at widest point (retrolateral axis), B
= conductor buttress, Cn = conductor, Cy = cymbium; T = tegulum. Adapted from Levi (1980).
Used by permission of the Museum of Comparative Zoology, Harvard University. Scale = 0.1 mm.

serving as controls were similarly handled but not cut. Females mated with these
control males were part of the Day 0 Sperm group.

Histological procedure. — Mated pairs in the Sperm groups were brought into
the lab five days following their initial copulation, ensuring that female sperm
storage sacs had hardened. The storage sacs were removed under a dissecting
microscope then placed in a 4 ml centrifuge tube with 200 ml of Ringer’s
solution. Following analyses on the image analyzer, male palps were treated in
the same manner. The palps (or sacs) were ground thoroughly with forceps and
then vortexed for approximately one min. The tubes were then centrifuged for 25
min at 1000 g. The tubes were removed, and the grinding, vortexing, and
centrifuging were repeated two more times. The tubes were vortexed one more
time, and then 5 ml samples were immediately removed, placed on acid-cleaned
gel-coated slides, dried ovenight, and stained with hematoxylin. In the study of
sperm availability in virgin males, the procedure was identical.

Sperm counts. — Sperm counts were performed on a Quantimet 970 Image
Analyzer®. To facilitate counting, 5 ml samples were used (2.5 percent of the
total). The image analyzer was programmed to count all objects with an area of
between 3 /x2 and 25 /i2. Within-field editing allowed for the exclusion of
extraneous material.

Egg sac analyses. — Following mating, females in the Egg groups were
maintained until oviposition. Egg sacs were brought into the lab approximately
five weeks after oviposition, sufficient time for spiderlings to have hatched and
molted to the second instar. Number of spiderlings, unhatched eggs, and egg sac
parasites were counted.

RESULTS

Palpal and gross morphological variation among mated males. — Overall palp
length (PLRA) ranged between 1.75 and 2.33 mm, a difference of about 25
percent. The distribution was normal with a skew of well under 1.00 (normality)

COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES

Table 1. — Mean (3c) and standard deviations (SD) for Day 0 and Day 14 subjects. The number of
sperm found in the male has been omitted from Day 0 data, as only a few sperm were found in only
two males. Sperm number refers to sample size (2.5% of the total) in Day 0 and Day 14 Sperm
subjects ( n = 35, 36 respectively). Percentage of clutch hatched refers to Day 0 and Day 14 Egg
subjects only ( n — 31, 38 respectively). PLRA = Palp length along retrolateral axis; CLPA =
Conductor length along prolateral axis; CLBB = conductor length below buttress; CndW =
Conductor width at widest point.

Day 0 (n

= 66)

Day 14 (n

= 74)

Measure

Cephalothorax abdomen (mm)

7.67

1.24

1A1

1.12

Tibia Patella (mm)

6.89

1.22

6.53

1.12

Weight (g)

0.033

0.016

0.028

0.010

PLRA (mm)

2.08

0.12

2.04

0.11

CLPA (mm)

1.60

0.07

1.58

0.08

CLBB (mm)

1.22

0.06

1.22

0.06

CndW (mm)

0.10

0.01

0.10

0.01

Sperm remaining in male palps

—

4401

4592

Sperm stored in females

8037

3682

1834

1404

Egg hatching percentage

0.90

0.24

0.88

0.27

In copula (min/h)

26.7

13.0

10.6

9.4

Hematodochal bulb contraction rate (n per min)

36.2

16.0

0.4

9.1

Female fends (per h)

21.4

16.2

1.7

7.0

Copulatory bouts (per h)

10.4

7.4

1.5

1.4

Palp pounds (bouts per h)

25.9

21.2

3.1

4.9

in Day 0 and Day 14 males. In comparison, tibia-patella length varied by over
100 percent, ranging between 4.0 and 9.4 mm. Indices of skewness and kurtosis
exhibited trivial differences from normality between all morphological measures.
Means and standard deviations for morphological and behavioral data are
presented in Table 1 .

Palps were less variable than more general measures of body size. This was
determined by calculating coefficients of variation (standard deviation/ (mean X
100)) and testing for significance using log transformations of each of the
morphological variables in Day 0 and Day 14 males. Log transformation allowed
the variance of each variable to be compared directly (Lewontin 1966). An F-
ratio was formed between the coefficient for each palpal measure and each gross
morphological measure. Coefficients for palpal measurements were significantly
smaller than those for weight, tibia-patella length, or cephalothorax-abdomen
length {p < 0.007). Among gross morphological variables, the coefficient for
weight was significantly larger than that for tibia-patella length or cephalothorax-
abdomen length (p < 0.001). Coefficients and variance of log transformed data
are presented for Day 0 and Day 14 subjects in Table 2.

There was a positive correlation between palp size and gross body size. The
highest correlation found was between PLRA and tibia-patella length in Day 14
subjects (r = 0.82; p < 0.00001).

Male size and available sperm in virgins. — In virgin males, the amount of
sperm found in palps was highly related to gross and palpal morphology. The
highest correlation was with weight (r = 0.82; p < 0.0001) and the lowest was
with tibia-patella length (r = 0.72; p = 0.002). The various measurements of palp
structure correlated equally with the amount of available sperm. Variables PLRA,
CLBB, and CndW correlated with sperm at r = 0.75 or 0.76 (p < 0.002). Variable

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Table 2. — Coefficients of variation (C. V.) (Mean/ (Standard deviation X 100)) and variance of gross
morphological and palpal measures using log transformation. CthA = cephalotharax-abdomen length;
TiPt =Tibia-Patella length; PLRA = Palp length along retrolateral axis; CLPA = Conductor length
along prolateral axis; CLBB — conductor length below buttress; CndW = Conductor width at widest
point.

Day 0

Day 14

Measure

c. v.

s2(Log«)

C. V.

s2(Log(*))

Gross

CthA

15.84

5.18X10"3

15.03

4.36X10~3

Weight

50.05

6.56X10-3

45.05

5.62X10-3

TiPt

19.05

8.12X10"2

17.30

4.04X10"2

Palp

PLRA

6.06

6.76X10

5.33

5.29X10

CLPA

4.62

4.00X10"4

4.91

4.41 X10"4

CLBB

5.01

5.29X10’4

4.90

4.4 IX IQ-4

CndW

7.11

5.29X10"4

7.71

4.41 X10-4

CLPA correlated with sperm at r — 0.61 (p — 0.009). Selection bias for very large
and very small males resulted in somewhat exaggerated Pearson’s rs.

Male size and sperm storage by females. — Male weight was the best predictor,
among male morphological characteristics, of the amount of sperm stored by the
female. Stepwise multiple regression performed on collapsed Day 0 and Day 14
data yielded a multiple R of 0.31 for the variable WGT. This score accounted for
a significant amount of the variance (F 2,68 = 7.42; p = 0.001). The variable
CthA accounted for a significant proportion of the remaining variance. When
included in the equation, CthA increased the multiple R to 0.41 ( F2,68 — 6.84;
p = 0.002). The relationships between male weight and the amount of sperm
stored by the female in Day 0 and Day 14 dyads are presented in Fig. 2.

Male size and proportion of sperm transferred. — When the amount of sperm
found in the female was expressed as a percentage of the total available sperm in
the female (SP-F) and male (SP-M) combined (SP-F/ (SP-M + SP-F)), no
significant relationships were found between the proportion of sperm found in the
female and any aspect of male morphology. To test whether males with average-
sized palps had an advantage over males of either extreme, proportions of sperm
transferred from Day 14 males were converted to z-scores and Pearson rs
calculated for the four palpal variables vs the z-scores’ absolute values. Once
again, no significant relationship was found.

Male size and copulatory behavior. — To examine whether small males exhibit
differences in copulatory behavior to compensate for a deficit in the ability to
facilitate sperm storage, the 10 largest (M CthA = 9.50; SD = 0.81) and 10
smallest (M CthA = 5.90; SD = 0.43) males were selected from the Day 0 groups
and the 1 1 largest (M CthA = 9.20; SD = 0.38) and 1 1 smallest (M CthA = 6.00;
SD = 0.57) from the Day 14 groups. Each group was divided in half again based
upon palp size (large or small palps using PLRA as an index), resulting in a 2 X 2
body size vs palp size design. Two-way analyses of variance were conducted to
determine whether these divisions resulted in significant size differences.

Day 0 subjects. — As expected, big males had significantly larger palps than
small males (FI, 16 = 196.904; p < 0.0001). When the data were collapsed across
body size, a significant difference was still found between the largest and smallest

COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES

Figure 2. — Scatterplot for male weight (g) and sperm (samples) found in female storage sacs in Day
0 and Day 14 dyads with regression lines. Pearson r for Day 0 animals = 0.46 (p = 0.0002).
Regression equation is Y = 5125 + 1.0163e+5x. For Day 14 animals the correlation is 0.25 (p = 0.05)
and the regression equation is Y = 991.1 + 3.1331e+4x.

palps (PLRA, large bodied males, M = 2.12; SD = 0.05; PLRA, small bodied
males, M = 1.81; SD = 0.04; FI, 16 = 44.109; p < 0.0001). The palp size X body
size interaction was not significant {p < 0.267). No behavioral differences related
to palp size or body weight were uncovered using MANOVA.

Day 14 subjects. — Large and small males displayed means and differences in
palp size nearly identical to those found in Day 0 males. Higher rates of some
copulatory behaviors were observed in larger males during the one hour serial
record: COP (FI, 18 = 5.98; p < 0.025), BOUT (FI, 18 = 4.77; p < 0.043), PP
(FI, 18 = 7.82; p < 0.012). The overall multivariate F of behavioral differences
based on male weight was significant (F6,13 = 3.83; p = 0.02). Higher rates of
palp pounding in large-palped males (FI, 18 = 18.58; p < 0.0004) and more
copulatory bouts (FI, 18 = 4.77; p < 0.043) contributed to a trend towards
significance in the multivariate F of differences based on palp size (F6,13 — 2.74;
p = 0.06). The overall multivariate F for the palp size by body weight interaction
was not significant {p = 0.34).

Male size and egg hatching. — Hatching percentage was not dependent upon the
size of the male. The highest correlation was with cephalothorax-abdomen length
in Day 0 subjects (r = 0.25; p = 0.05). This relationship was not apparent in the
Day 14 Egg group.

Female age at mating, sperm storage, and copulatory behavior. — When mating
with a newly-molted female, males nearly always transferred their entire supply of
sperm (M > 99 percent). When copulation was delayed for two weeks, mated
males retained about 24 percent of the sperm found in virgin males. A one-way
analysis of variance between Sperm groups indicated that significantly more
sperm were found in Day 0 females (FI ,69 = 35.70; p < 0.0001). A mean of 8037
sperm was found in Day 0 samples (SD = 3682), versus 1834 in Day 14 samples

THE JOURNAL OF ARACHNOLOGY

(SD = 1404). These means reflect sample sizes of 2.5 percent of the total sperm.
When the number of sperm transferred to Day 14 females was expressed as a
percentage of the total available sperm (SP-F/(SP-M + SP-F)), no relationship
was found to exist between any of the behavioral variables and the proportion of
sperm transferred.

A MANOVA was performed to determine if any aspects of copulatory activity
were related to female age at mating. Due to missing data, three dyads were
dropped (for this analysis only) leaving a total of 137. The overall multivariate F
was significant (F14,122 — 24.75; p < 0.0001), indicating that the overall pattern
of variable scores differed between Day 0 and Day 14 subjects. Subsequent
analyses revealed significantly higher rates of copulatory activity in Day 0
subjects: more time spent copulating per one hour serial record (FI, 135 = 68.87;
p < 0.0001), a higher number of copulatory bouts (FI, 135 = 105.79; p < 0.0001),
higher rate of hematodochal bulb contractions (FI, 135 = 143.50; p < 0.0001),
and more palp pounding (FI, 135 — 77.40; p < 0.0001). There were more fends by
the female as well (FI, 135 = 87.73; p < 0.0001).

Females fended males more often per unit time spent copulating on Day 0
(FI, 115 = 10.498; p < 0.002); the mean fend/ cop ratio was 1.04 on Day 0 versus
0.33 on Day 14. Cases where no copulations were observed during the one hour
observation period were dropped from this analysis ( N = 23) leaving a final N of
117. To determine if females were influencing the number of times a male
attempted to mate, 10 Day 0 dyads and 10 Day 14 dyads were randomly selected
from those dyads in which at least one mating attempt and fend were observed.
The above analysis was then repeated using the ratio of fends to copulatory
attempts. A copulatory attempt was defined as occurring when the male
descended to the ventrum of the female followed by either successful copulation
or insertion of less than 5 sec. No significant difference was found between Day 0
and Day 14 dyads (p = 0.346). Day 0 males were fended a mean of 1.1 times per
copulatory attempt. Day 14 males were fended a mean of 0.8 times per attempt.

Do females influence copulation duration? — Gross female activity had little
effect on male reproductive behavior. Female fends of males were not correlated
with the amount of copulation and only a slight negative correlation was found
with the amount of sperm later obtained in the female (Day 0 r = —0.23; p =
0.06; Day 14 r = —0.26; p = 0.05). Fends were positively correlated with BC rates
in Day 0 males (r = 0.38; p = 0.001), but this relationship was not found in Day
14 dyads.

Copulatory behavior and sperm storage. — Among Day 0 subjects, total
copulation time was the best behavioral predictor of the amount of sperm found
in the female. This variable had a correlation with SP-F of 0.47, and was the only
variable accounting for a significant proportion of the total variance (FI, 32 =
8.89; p < 0.001). No behavioral variables were related to the amount of sperm
found among Day 14 females. The predictive value of behavioral variables were
determined by stepwise multiple regression analysis. Because of behavioral
differences between Day 0 and Day 14 mating, the analysis was run under each
condition.

Amount of sperm transferred during feeding bouts. — Day 14 Sperm dyads were
analyzed to determine how much sperm were transferred during each mating
bout. These copulations took place almost exclusively after mealworms were
added and when females were observed feeding. The numbers of bouts are only

COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES

an approximation as clearly not every one occurring within these dyads was
recorded. In three cases, sperm were found in females even though no copulation
was observed. Because final molts were observed, it is clear that insemination
could only have been carried out by the introduced males. These dyads were
included and scored as having the minimum possible one copulatory bout. A
mean of 2.8 copulatory bouts were observed among Day 14 Sperm subjects over
the 4 days of observations (SD = 1.6). Each bout resulted in the transfer of a
mean of 37 750 sperm (SD = 46 886). These were the true numbers, obtained by
multiplying the sample size by 40. As the mean amount of sperm found in virgin
males (total, not sample size) was 520 898 (SD = 257 779), each bout transferred
about seven percent of the male’s total sperm. There was, however, a large
amount of variation among males.

“Lost” sperm. — Because the combination of SP-F and SP-M always appeared
to be less than the amount of sperm found in similarly-sized virgin males, a
comparison was made between the two totals. Seventeen mated males were
matched for weight with the virgin males. Virgin males contained significantly
more sperm than were found in mated pairs (FI ,34 — 17.64; p — 0.0002). There
was a mean of 13 022 sperm in the virgin male samples (SD = 6444) and 6261 in
the mated pair samples (SD = 2647). There was no significant difference in
weight between the mated and virgin males (M = 0.029 g and 0.021 g,
respectively), hence a reasonable matching (p = 0.30).

Copulatory behavior, time of mating, and egg hatching. — Egg hatching
percentage was not greatly influenced by male behavior. The highest correlation
found was with hematodochal bulb contraction rate (r = 0.25; p = 0.05). This
correlation was identical for both the Day 0 and the Day 14 groups. Females of
both groups had a mean 89 percent of their clutch hatch. Time of mating did not
affect egg hatching percentage (p = 0.727).

Differences in egg parasitism between Day 0 and Day 14 clutches. — Many egg
sacs contained parasites. The majority were larvae of the insect family
Mantispidae. One sac contained a small unidentified spider. Twelve of 31 Day 0
egg sacs (39%) were found to contain at least one parasite. Nine of 38 Day 14 egg
sacs (24%) were also parasitized. Chi-square analysis indicated no significant
association of time of mating with rates of egg parasitism (p = 0.177).

Frequency of conductor breakage. — Only the first 100 virgin males collected for
this study were checked for broken conductors prior to their introduction to
females. Four had a broken conductor tip and were excluded. When the 140
mated males included in this study (excluding those that were artificially broken)
were examined, eight had a single broken conductor. No males had two broken
conductors. Chi-square analysis indicated that conductor breakage was equally
likely in virgin and non-virgin males (p = 0.54). Chi-square analysis further
indicated that, following mating, sperm remaining in males with broken
conductors equalled that of intact males matched for weight and time of mating
{p = 0.59). As conductors were not found to be broken more frequently following
mating, it is clear that copulation is not a major cause of conductor breakage.

Cut palp study. — Severing the tips of conductors had adverse effects on male
reproductive behavior. Hematodochal bulb contractions, an index of copulation
intensity, were observed in only two of the experimental males tested. A small
amount of sperm (about 250/ sample) were found in one female paired with a cut
male. A MANOVA was performed to evaluate differences in copulatory behavior

THE JOURNAL OF ARACHNOLOGY

between these two groups. The overall multivariate F was significant (T9, 9 =
9.49; p = 0.001). Intact males were observed copulating significantly more often
than cut palp animals (FI, 17 = 29.08; p < 0.0001). Hematodochal bulb
contractions were significantly faster in intact males as well (FI, 17 = 7.31; p =
0.015). The damaged palp was clearly preventing successful copulation. This was
also reflected in the number of copulatory bouts (FI, 17 = 19.73; p = 0.0004).
Motivation to mate, however, seemed unaffected. The number of copulatory
attempts made by the males were compared to evaluate whether damaged males
were less active. There was no significant difference between intact and cut palp
males (p = 0.65) nor were differences in palp pounding observed {p = 0.19).
Females did not distinguish between intact and damaged males. Cut palp males
were not fended away any more often than intact males (p — 0.12). Behavioral
data for cut palp and intact males are presented in Table 3.

DISCUSSION

Palpal Variation and its relation to gross male morphology. — Variation in palp
size does not exhibit a range comparable to that found in more gross
measurements such as weight or cephalothorax-abdomen length. Small males
with exceptionally large palps or large males with small palps were not observed
in the sample studied. The reduced variance in palpal size is consistent with
results obtained in other genera such as Pardosa (Barnes 1959), Castianeira
(Reiskind 1969), and Hypochilus (Coyle 1985). This consistency is an important
reason for the use of male genitalia as taxonomic markers (McCrone 1963; Coyle
1985), and suggests that any selective forces at work favor a narrow range of palp
sizes rather than a trend towards ever larger (or smaller) palps. While there are
likely to be genetic constraints on the overall size of males, there appear to be
stronger constraints on palp size. Ecological variables such as prey availability
and temperature exert a much stronger influence on gross morphology than on
palp morphology (Vollrath 1980). Growth rates among unrestrained populations
during critical periods of development are highly variable, changing with shifts in
these factors (Coyle 1985).

Determinants of sperm storage by males and females, and its utilization. — The
amount of sperm stored in male palps prior to mating is closely related to overall
male size. The correlation between size and sperm availability could be due to
two factors. Larger males probably have more gonadal tissue with which to
manufacture sperm and larger palps in which to store sperm until the opportunity
to mate arises.

The amount of sperm stored by female N. clavipes is related to the gross size of
the male and to the size of his palps. When the amount of sperm found in Day
14 females was expressed as a percentage of the total, however, no advantage was
found for exceptionally large, small, or average-sized males. As a large
proportion of the available sperm was “misplaced” somewhere between
copulation and laboratory analysis, this statement is made with some caution.

Twice as many sperm were present in virgin males as were later recovered from
mated dyads. Some of the difference in numbers can be attributed to
experimental procedures as the SP-M + SP-F group went through the sperm
counting procedure twice and the virgin male group once. Sperm taken from

COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES

Table 3. — Descriptive statistics for intact and cut palp males in the conductor manipulation study.
N = 19. 3c = Mean; SD = Standard deviation.

Measure

Intact palp

Cut palp

Copulatory attempts (per h)

21.67

13.13

19.22

20.36

Palp pounds (bouts/ h)

32.67

33.46

15.90

18.73

In copula (min per h)

22.00

11.47

1.67

3.54

Copulatory bouts (per h)

8.33

5.20

0.80

1.32

Hematodochal bulb contraction rate (n per min)

34.00

16.08

11.00

22.51

Female fends (per h)

23.00

20.37

10.78

14.65

females also had a tendency to clump together occasionally, sometimes making an
accurate count more difficult. However, the very large difference indicates some
loss of sperm and warrants further investigation.

Male body size, palp size, and behavior were not related to the percentage of
eggs hatching. This is logical as females were not mated with second males and
may be expected to use any sperm available to them at the time of oviposition. It
remains to be seen whether the aforementioned variables influence paternity when
females mate with more than one male.

Timing of the initial copulation. — The timing of mating greatly influences
copulatory behavior and the amount of sperm ultimately stored by the female.
These results are consistent with past studies of N. clavipes (Brown 1985;
Christenson et al. 1985). There was no reduction in female reproductive success
when her initial mating was delayed for two weeks. Surprisingly, females fended
off males significantly more often just after molting. This is in part due to the
increased amount of copulatory behavior occurring at this time. When the
proportion of fends to observed copulation time is compared for the two groups,
however, it is clear that females were more reactive following the final molt.

Females in the Day 14 Egg group fertilized their entire clutch despite receiving
only 24 percent of the males’ sperm. This is interesting as it calls into question
why a male transfers his entire supply of sperm when mating with a newly-molted
adult. Some recent modeling by T. E. Christenson and W. P. Dunlap (Pers.
comm.) proposes that total sperm transfer is the best strategy for a male mating
with a newly-molted adult. Their model suggests that total transfer may be a
consequence of the extended copulation necessary to insure a first male
precedence effect (Christenson and Cohn 1988). One advantage may be to dilute
the effectiveness of subsequent mating by the female. Sperm “dumping” may also
result from the rather low probability of successful copulation (about 20 percent
of males) and the even lower probability of a mated male either making it to the
hub of another receptive female or defending his mated partner until oviposition
(unpublished data).

Conductor breakage. — Conductor breakage did not occur in mated males at a
higher rate than in virgins. The overall rate of breakage was low, less than seven
percent. While the occasional broken conductor tip may inhibit further sperm
uptake, the low rate of breakage suggests that this is not a typical occurrence.
When conductor tips were experimentally severed, behavioral deficits were
observed. Males with severed conductors did not mate successfully as only one
male transferred a small number of sperm. Motivation to mate seemed unaffected

THE JOURNAL OF ARACHNOLOGY

as there were no significant differences in the number of copulatory attempts or
palp pounds.

Male copulatory behavior, morphology, and uptake. — The copulatory
behaviors evaluated in this study did not vary systematically with either male size
or uptake of sperm by the female. Hematodochal bulb contraction rates were
higher in Day 0 males, and females in this group acquired more sperm. These
differences seem to be related to the softer, unscleroticized epigynal tissues in
newly-molted females and not to individual male variation (Christenson and
Cohn 1988). Among Day 0 subjects, copulation time correlated most strongly
with the number of sperm found in the female. This is surprising as all males in
this group were virtually depleted of sperm. These results, and the finding that a
good deal of sperm may be Mlost”, suggest that increased amounts of copulatory
activity could facilitate storage of sperm and not just release. However, no
relationship was found between observed copulation time and the amount of
sperm later found in Day 14 females. These results suggest that larger amounts of
sperm simply take longer to transfer. In N. clavipes , however, all sperm is
transferred within the first three hours while copulation continues for up to 48 h
(Christenson and Cohn 1988). It seems unlikely, therefore, that the higher
proportion of time larger males spent in copula was due to the volume of sperm
they carried. The meaningfuleess of the relationship between copulation time and
sperm storage by the female remains unclear. Twenty-four h serial records need
to be conducted on older adult females mating for the first time, with sampling of
the amount of sperm found in each member of the dyad occurring at different
times after the first observed copulation. Time sampling methodology as
employed in the present study may not be able to yield data of sufficient
accuracy.

Sexual selection in N. clavipes. — The following conclusions can be drawn
regarding sexual selection in N. clavipes. Intense intrasexual selection, through
agonistic encounters among males, takes place before, during, and after
copulation (Goist 1983; Cohn et al 1988). No evidence for intersexual selection
was found in the present study. This investigation was, however, conducted
within very narrow parameters, during and immediately after mating with a single
male. Female N. clavipes can, of course, influence their reproductive processes in
ways not addressed in the present study. For example, Christenson and Cohn
(1988) demonstrated that the first male advantage typical in N. clavipes can be
significantly reduced if males are limited in the amount of copulation time
following sperm transfer. Post-transfer copulation may reduce future sexual
receptivity in the female (Christenson and Cohn 1988). Fifteen percent of females
leave their orb within 24 h of their final molt with little likelihood of successful
pursuit by the male (Cohn et al 1988). These early departures may provide a
means for intersexual selection to operate.

In summary, a close relationship was found between the size of the male, the
amount of sperm available for transfer, and the amount of sperm later found in
the females5 storage sacs. Females who mate with the largest males store the most
sperm, but even the smallest males transfer enough to fertilize a clutch. While
female N. clavipes may exercise several reproductive options, no preference for
males of a particular size was found within the parameters of this study.

COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES

ACKNOWLEDGEMENTS

I would like to thank T. E. Christenson for his guidance and support during
the course of this study. I would also like to thank H. W. Levi for his permission
to include figures from one of his publications, W. G. Eberhard and S. N. Austad
for their comments and suggestions, and the many field and laboratory assistants
without whom this work could not have been done.

LITERATURE CITED

Barnes, R. D. 1959. The lapidicina group of the wolf spider genus Pardosa (Araneae, Lycosidae). Am.
Mus. Nov., 1960:1-20.

Brown, S. G. 1985. Mating behavior of the golden orb-weaving spider, Nephila clavipes: II. Sperm
capacitation, sperm competition, and fecundity. J. Comp. Psychol., 99:167-175.

Christenson. T. E. and K. C. Goist. 1979. Costs and benefits of male-male competition in the orb-
weaving spider, Nephila clavipes, Behav. Ecol. Soeiobiol., 5:87-92.

Christenson, T. E. 1984. Alternative reproductive tactics in spiders. Amer. Zool. 24:321-332.

Christenson. T. E., S. G. Brown, P. A. Wenzl, E. M. Hill and K. C. Goist. 1985. Mating behavior of
the golden orb-weaving spider. Nephila clavipes: I. Female receptivity and male courtship. J.
Comp. Psychol., 99:160-166.

Christenson, T. E. and J. Cohn. 1988. Male advantage for egg fertilization in the golden orbweaving
spider. J. Comp. Psychol., 102:312-318.

Cohn, J. and T. E. Christenson. 1987. Resource utilization in the male golden orb-weaver Nephila
clavipes. J. Arachnol., 15: 185-192.

Cohn, J., F. V. Balding and T. E. Christenson. 1988. In defense of Nephila : Post-mate defense in the
golden orb-weaving spider. J. Comp. Psychol., 102:319-325.

Coyle, F. A. 1985. Two-year life cycle and low palpal character variance in a great smoky mountain
population of the lamp-shade spider (Araneae, Hypochilidae, Hypochilus). J. Arachnol., 13:211-
218.

Eberhard, W. G. 1985. Sexual Selection and Animal Genitalia. Harvard University Press, Cambridge.
Eberhard, W. G. 1986. Why are genitalia good species characters? Int. Congr. Arachnol, 9:53-59.

Goist, K. C. 1983. Male-male competition in the orb weaving spider. Nephila clavipes. Unpublished
doctoral dissertation, Tulane University, New Orleans, Louisiana.

Jackson, R. R. 1980. The mating strategy of Phidippus johnsoni (Araneae, Salticidae): II. Sperm
competition and the function of copulation. J. Arachnol. 8:217-240.

Levi, H. W. 1980. The orb-weaver genus Mecynogea, the subfamily metinae and the genera
Pachygnatha, Glenognatha, and Azilia of the subfamily tetragnathinae north of Mexico (Araneae:
Araneidae). Bull Mus. Comp. Zool, 149:1-75.

Lewontin, R. C. 1966. On the measurements of relative variability. Syst. Zool., 15:141-142.

McCrone. J. D. 1963. Taxonomic status and evolutionary history of the Geolycosa pikei complex in
the southeastern United States (Araneae, Lycosidae). Am. Midi. Nat., 70:47-73.

Moore. C. W. 1977. The life cycle, habitat, and variation in selected web parameters in the spider
Nephila clavipes Koch (Araneidae). Am. Midi. Nat., 98:95-108.

Myers, L. and T. E. Christenson. 1988. Transition from predatory juvenile male to mate-searching
adult in the orb-weaving spider Nephila clavipes (Araneae, Araneidae). J. Arachnol, 16:254-257.
Reiskind, J. 1969. The spider subfamily castianeirinae of North and Central America (Araneae,
Clubionidae). Bull Mus. Comp. Zool, 138:163-325.

Robinson. M. H. and B. Robinson. 1980. Comparative studies of the courtship and mating behavior
of tropical araneid spiders. Pac. Ins. Monogr., No. 36. Bishop Museum, Honolulu.

Robinson, M. H. 1982. Courtship and mating behavior in spiders. Ann. Rev. Entomol, 27:1-20.

Schult, J. and U. Sellenschlo. 1983. Morpholgie und funktion der genitalstrukturen bei Nephila
(Arach., Aran., Araneidae). Mitt. Ham. Zool Mus. Inst., 80:221-230.

Thornhill, R. and J. Alcock. 1983. The Evolution of Insect Mating Systems. Harvard University
Press, Cambridge.

Vollrath, F. 1980. Male body size and fitness in the web-building spider Nephila clavipes. Zeit. F.
Tierpsychol, 53:61-78.

Manuscript received August 1988 , revised June 1989.

Anderson, J. E 1990. The size of spider eggs and estimates of their energy content. J. Arachnol,
18:73-78.

THE SIZE OF SPIDER EGGS AND
ESTIMATES OF THEIR ENERGY CONTENT

John F. Anderson

Department of Zoology
University of Florida
Gainesville, Florida 32611 USA

ABSTRACT

Egg size was used to estimate the energy incorporated into egg production in a sample of 24 species
representing 1 1 families. Egg mass scaled geometrically to egg diameter. Egg mass can be accurately
estimated from the easily measured diameter of an egg. Comparison of egg sizes between populations
of seven species common to Connecticut and Florida suggest egg size is species-specific. The constancy
of energy density of spider eggs allows relatively accurate estimates of the energy incorporated into
egg production using easily obtained data on egg size, number of eggs per clutch, and number of
clutches.

INTRODUCTION

A basic consideration in most studies of spider reproduction relates egg
production to energy availability (Craig 1987). In general, the number of clutches
and number of eggs per clutch is determined by food supply (Bristowe 1958;
Riechert and Tracy 1975; Enders 1976; Eberhard 1979; Craig 1987).

Studies emphasizing energetic costs of producing eggs exhibit a potential
problem, namely the difficulty of measuring all the components necessary to
estimate such costs. Single indices such as egg number (Petersen 1950; Enders
1976; Valerio 1976; Miyashita 1987a, b; Roach 1988; DeKeer and Maelfait 1988)
and egg mass (Taylor and Peck 1975; Riechert and Tracy 1975; Killebrew and
Ford 1985; Morse 1987) have been used as estimates of the energy incorporated
into egg production. Use of single indices requires certain assumptions to make
valid comparisons. For example, comparison of egg number assumes egg sizes are
equal among the compared groups. A complete estimate of such costs over the
life span of a female spider requires data on the number of clutches, the number
of eggs per clutch, egg size, and energy density of the eggs. The fact that these
studies are incomplete in this context is evidence of the very real difficulties of
obtaining such data.

A major problem in this context is measurement of energy density. Accurate
estimates using bomb calorimetry are time consuming and require skill,
dedication, and careful attention to numerous procedural details (Phillipson 1964;
Paine 1971; Anderson 1978). The time and labor involved justifies search of other
methods of estimating relative energy content of eggs. Analysis of inter- and
intraspecific variation of clutch size, egg size, and energy density indicate the

THE JOURNAL OF ARACHNOLOGY

latter is the least variable (Anderson 1978), Killebrew and Ford (1985) argued
that mass per newly hatched spiderling, and by extension, egg mass, in any one
species is “optimized by natural selection.” If correct, egg size might provide a
practical and reasonably accurate measure of the energy content of a spider egg.

Here I evaluate egg size, measured as a linear dimension, to estimate egg mass.
Linear dimensions of eggs can be easily and accurately measured using dissecting
microscopes common to most laboratories. My specific aims were to determine
whether egg size is species-specific and, if so, to describe the relationship between
diameter and egg mass.

METHODS AND MATERIALS

Egg sacs of various species were collected from habitats around Gainesville,
Florida. Although I picked species based on availability of reproductively active
females, some effort was made to choose those which provide a reasonable range
in the measured parameters. Of the 24 species considered here, data for 12 were
obtained from a previous study (Anderson 1978).

Eggs were removed from egg sacs and counted. Their total wet mass was
immediately measured to the nearest 0.1 mg and the average mass per egg
determined by calculation. Egg diameter was measured to the nearest 0.01 mm
with a dissecting microscope fitted with a calibrated ocular on a minimum of ten
eggs per egg sac. Since few eggs are exactly spherical, the reported diameters
represent the average of measurements made on the longest and the shortest axis
of an egg. Differences between these two measurements of all samples averaged
7%.

Assuming geometric similarity obtains, i.e., shape and density are constant, the
mass of an egg would be proportional to diameter3 where the latter represents a
characteristic linear dimension (McMahon and Bonner 1983). Consequently I
fitted the data to the power function EM — aEDb. Here EM represents egg wet
mass; ED is egg diameter; a is a proportionality constant and b is the exponent
of the function. The parameters a and b were calculated by least squares analysis
of paired data after transformation to common logarithms. Correction for bias in
log-transformed data (Sprugel 1983) made in estimating the proportionality
constant (a) produced a result not different from the uncorrected value. The
standard error (St) and 95% confidence limits for b, r2, and Sy*x were calculated
as indices of fit of the regression as recommended by Smith (1984).

RESULTS AND DISCUSSION

The data collected from 24 species representing 11 spider families (Table 1)
show much variation. The largest female is 112 times the smallest in the sample;
number of eggs per clutch, egg diameter, and egg mass exhibit 39-, 2.8-, and 17.5-
fold variation in the these measures, respectively.

A good fit exists between egg mass and egg diameter (Fig. 1). The coefficient of
determination (r2) is 0.99 and indicates the fraction of variation in egg mass
explained by variation in egg diameter. The standard error of the estimate (Sy*x),
standard error (s*>) and 95% confidence limits for b are 0.035, 0.066, and 2.77-
3.05, respectively. Support for the predictive ability of the model is provided by

ANDERSON— EGG SIZE AND ENERGY CONTENT

Table 1. — Number, size, and mass of spider eggs. Data are averages (+/— SD).

Sample

FAMILY size

Species (clutches)

Female
live mass
(mg)

Number of
eggs per
clutch

Egg

diameter

(mm)

Egg

live mass
(mg)

FILISTATIDAE

Filistata hibernalis

347 (188)

129 (63)

1.37 (0.05)

1.42 (0.01)

Physocyclus species

28.9 (8.0)

73 (9.2)

0.82 (0.01)

0.31 (0.03)

THERIDIIDAE

Achaearanea tepidariorum

37.7(19.3)

149 (55)

0.59 (0.01)

0.12(0.01)

Argyrodes trigonum

10.9

0.67

0.17

Tidarren sisyphoides

51.8

238

0.66

0.16

ARANEIDAE

Acanthepeira stellata

596

574

1.04

0.55

Acanthepeira venusta

182 (72)

232 (70)

0.88 (0.02)

0.34 (0.02)

Argiope aurantia

752

978

0.92

0.46

Gasteracantha elipsoides

175

195

0.81

0.25

Mecynogea lemniscata

59.9(11.1)

25 (5.3)

1.01 (0.01)

0.54 (0.04)

Metazygia wittfeldae

87.0 (29.9)

84 (31)

1.06 (0.07)

0.51 (0.08)

Nuctenea cornuta

263 (52)

484(130)

1.00 (0.02)

0.49 (0.05)

AGELENIDAE

Agelenopsis barrowsi

138

0.98

0.47

PISAURIDAE

Pisaurina mira

293 (78)

264 (207)

1.15(0.09)

0.78 (0.09)

LYCOSIDAE

Lycosa lenta

1007 (234)

302 (48)

1.45 (0.05)

1.59 (0.15)

OXYOPIDAE

Peucetia viridans

348 (22)

382 (36)

1.48 (0.02)

1.77 (0.08)

SPARASSIDAE

Heteropoda venatoria

1221

184

1.66

2.10

THOMISIDAE

Misumenoides formosipes

117

552

1.01

0.47

Misumenops celer

28.1

0.78

0.25

SALTICIDAE

Eris marginata

43.1

0.93

0.37

Phidippus audax

223 (29.3)

186 (69)

1.26 (0.05)

1.03 (0.09)

Phidippus pulcherrimus

75.1 (9.0)

76(15)

1.25 (0.01)

1.00 (0.08)

Phidippus regius

570

439

1.29

1.17

Thiodina sylvana

44.9

1.08

0.69

Wise’s (1973) data on egg dimensions of Linyphia marginata. Given the reported
diameter for these eggs, the equation (Fig. 1) predicts a wet weight equal to that
indicated.

Although egg size exhibits much variation interspecifically (Table 1), I was
impressed by the constancy of this measure within a species (see also Anderson
1978; Killebrew and Ford 1985). For example, the coefficients of variation
involving egg diameter within each of the 12 species where multiple samples were
available average 3.0% (Table 1). Conversely, the coefficient of variation for
average egg diameter of the same 12 species is 24.3%. If egg size is species-
dependent and not subject to environmental influences, egg sizes of the same
species from different populations should not differ from one another. Such a
comparison was made using the appropriate data from Kaston (1981) for
Connecticut populations of seven species in common (Table 2). Analysis of the
paired data indicate no significant differences exist (P = 0.94) in egg size. The

THE JOURNAL OF ARACHNOLOGY

Figure 1. — Relationship between wet mass of egg (EM) and egg diameter (ED).

constancy of egg size provides validity to those studies comparing numbers of
eggs or total egg mass as is so common in intraspecific studies.

The accuracy of estimates of the amount of energy incorporated into egg
production made from number of clutches, number of eggs and their weight
would depend on variation in energy density of eggs. Although variation in this
measure is biologically significant and is correlated with the early life history
patterns of individual species, the magnitude of this variation is not large
(Anderson 1978). The reported values for the 12 species studied range from 26.3
to 29.0 joules per mg ash-free dry weight with an average of 27.3. Dry weight and

Table 2. — Comparison of egg size in spiders from Connecticut (Kaston 1981) and Florida (this

study).

Species

Egg diameter (in mm)

Connecticut

Florida

A. tepidariorum

0.55

0.59

A. trigonum

0.65

0.67

A. aurantia

1.00

0.92

N. cornuta

1.00

1.15

P. mira

1.20

1.15

M. formosipes

0.96

1.01

P. audax

1.22

1.26

ANDERSON— EGG SIZE AND ENERGY CONTENT

ash content of spider eggs are 31.9 and 3.58% of wet weight, respectively
(Anderson 1978). Relative to the average, the potential error associated with the
highest and lowest value are 6.2 and 3.7%, respectively. Since variation in the
other variables such as number of clutches, number of eggs, and egg size is
usually much larger, assuming a constant energy density would provide
reasonably accurate comparative estimates of the energy incorporated into egg
production in most cases. Certainly the number of egg sacs, number of eggs, and
egg size can be counted and measured with ease and accuracy thus permitting
more extensive studies of the energetics of reproductive output than would
otherwise be practical.

ACKNOWLEDGMENTS

I wish to thank C. Binello and G. Kiltie for typing the manuscript, D. Harrison
for aid in constructing the figure, and both reviewers for their constructive
suggestions.

LITERATURE CITED

Anderson, J. F. 1978. Energy content of spider eggs. Oecologia, 37:41-57.

Bristowe, W. S. 1958. The World of Spiders. Collins, London.

Craig, C. L. 1987. The significance of spider size to the diversification of spider-web architectures and
spider reproductive modes. American Natur., 129:47-68.

DeKeer, R. and J. F. Maelfait. 1988. Laboratory observations on the development and reproduction
of Erigone atra Blackwall, 1833 (Araneae, Linyphiidae). Bull. British Arachnol. Soc., 7:237-242.

Eberhard, W. G. 1979. Rates of egg production by tropical spiders in the field. Biotropica, 11:292-300.

Enders, F. 1978. Clutch size related to hunting manner of spider species. Ann. Entomol. Soc.
America, 69:991-998.

Kaston, B. J. 1981. Spiders of Connecticut. 2nd ed. Connecticut State Geol. Natur. Hist. Survey. Bull.
No. 70.

Killebrew, D. W. and N. B. Ford. 1985. Reproductive tactics and female body size in the green lynx
spider, Peucetia viridans (Araneae, Oxyopidae). J. Arachnol., 13:375-382.

McMahon, T. A. and J. T. Bonner. 1983. On Size and Life. Sci. American Books, New York.

Miyashita, K. 1987a. Development and egg sac production of Achaearanea tepidariorum (C. L. Koch)
(Araneae, Theridiidae) under long and short photoperiods. J. Arachnol., 15:51-58.

Miyashita, K. 1987b. Egg production of Achaearanea tepidariorum (C. L. Koch) (Araneae,
Theridiidae) in the field in Japan. J. Arachnol., 15:130-132.

Morse, D. H. 1987. Attendance patterns, prey capture, changes in mass, and survival of crab spiders
Misumena vatia (Araneae, Thomisidae) guarding their nests. J. Arachnol., 15:193-204.

Paine, R. T. 1971. The measurement and application of the calorie to ecological problems. Ann. Rev.
Ecol. System., 2:145-164.

Petersen, B. 1950. The relation between size of mother and number of eggs and young in some spiders
and its significance for the evolution of size. Experientia, 6:96-98.

Phillipson, J. 1964. A miniature bomb calorimeter for small biological samples. Oikos, 15:130-139.

Riechert, S. E. and C. R. Tracy. 1975. Thermal balance and prey availability: bases for a model
relating web-site characteristics to spider reproductive success. Ecology, 56:265-284.

Roach, S. H. 1988. Reproductive periods of Phidippus species (Araneae, Salticidae) in South
Carolina. J. Arachnol, 16:95-101.

Smith, R. J. 1984. Allometric scaling in comparative biology: problems of concept and method.
American J. Physiol, 246:R152-R160.

Sprugel, D. G. 1983. Correcting for bias in log-transformed allometric equations. Ecology, 64:209-210.

Taylor, B. B. and W. B. Peck. 1975. A comparison of northern and southern forms of Phidippus
audax (Hentz) (Araneida, Salticidae). J. Arachnol, 2:89-99.

THE JOURNAL OF ARACHNOLOGY

Valerio, C. E. 1976. Egg production and frequency of oviposition in Achaearanea tepidariorum
(Araneae, Theridiidae). Bull. British Arachnol. Soc., 3:194-198.

Wise, D. H. 1973. Egg cocoon of the filmy dome spider Linyphia marginata C. L. Koch (Araneae:
Linyphiidae). J. Arachnol., 1:143-144.

Manuscript received June 1989, revised September 1989.

Paz S., N. and R. J. Raven. A new species of Linothele from Colombia (Araneae, Mygalomorphae,
Dipluridae). J. Arachnol., 18:79-86.

A NEW SPECIES OF LINOTHELE FROM COLOMBIA
(ARANEAE, MYGALOMORPHAE, DIPLURIDAE)

Nicolas Paz S.

Depto. de Biologia, Universidad de Antioquia
Medellin, Colombia

Robert J. Raven

Queensland Museum
P.O. Box 300, South Brisbane, 4101
Queensland, Australia

ABSTRACT

Linothele megatheloides is newly described from Colombia. It differs from other species of
Linothele by the larger size, very long posterior lateral spinnerets and scopulate tarsi of females.

INTRODUCTION

Linothele is one of three diplurid genera that build conspicuous webs in South
and Central America (see Paz S. 1988); the others are Diplura , with which it was
long confused (see Raven 1985), and Ischnothele. Spiders of these genera build
expansive sheet webs leading to a funnel in overhangs of banks and shelters
formed by tree buttresses (Coyle 1986). The web includes numerous large
corridors through which the spider runs while holding the very long spinnerets
high above the abdomen. Paz S. (1988) has discussed the behavior and ecological
aspects of this new species. All measurements are in millimeters and abbreviations
are standard for the Araneae.

Linothele megatheloides , new species

Figs. M2

Types. — Holotype male, paratype female from Tutunendo, Choco, Colombia,
(27 July 1983; N. Paz S.), deposited in the American Museum of Natural History.

Etymology. — The specific epithet refers to the very long posterior lateral
spinnerets.

Diagnosis. — L. megatheloides differs from L. macrothelifera Strand, 1908 (type
in Senckenberg Museum, Frankfurt, examined), which also has long spinnerets,
in the much larger size, very long spinnerets (Fig. 9), pseudosegmented apical
article of posterior lateral spinnerets, and the presence of some scopulae on tarsi
of females.

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Figures 1-4. — Linothele megatheloides, female. Scanning electron micrographs: 1, 2, tarsus I
(shaved) showing pseudosegmentations; 3, cuticle and trichobothrial base with shallow corrugations; 4,
ventral “scopula” hair.

Description. — Holotype male: (Figs. 5-8, 12). Total length, including chelicerae,
33. Carapace red brown, striae marked by black reticulations along edges; caput
brown with donut-shaped darkened ring medially; chelicerae, and legs red brown.
Dorsum of abdomen brown with two lighter colored longitudinal bands, venter
brown.

Carapace 10.83 long, 9.83 wide; with fine black hairs and bushy band of black
hairs on margins. Foveal bristles absent; one long bristle between PME, four long
on clypeal edge; 4 long between PME; no anteromedial bristles; few in striae;
striae distinct. Fovea short, recurved; clypeus absent.

Eight eyes on tubercle occupying about 0.50 of front width. Ratio of eyes,
anterior lateral: anterior median: posterior lateral: posterior median, 34:33:25:18.
Anterior row slightly procurved; medians separated by 0.2 of their diameter, 0.2
from laterals. Posterior row recurved, medians separated by 1.6 times AME
diameter, 0.2 from laterals. Median ocular quadrangle wider than long (74/46),
narrower in front (61/74). Lateral eyes of each side separated by 0.2 of AME
diameter.

Sternum 4.08 long, 4.06 wide; covered with long erect black bristles mixed with
fine hairs; sigilla oval to subcircular, marginal. Labium 1 .44 long, 2.00 wide, with
no cuspules. Palpal coxae 3.20 long behind, 2.96 long in front, 1.36 wide, with
28-30 cuspules (not on mound) on inner angle; anterior lobe indistinct. Chelicerae
small, slender, with dorsal band of fine brown hair and few black bristles;

PAZ & RAVEN— A NEW SPECIES OF LINOTHELE

Figures 5, 6. — Linothele megatheloides , holotype male: 5, carapace and chelicerae, dorsal view; 6,
tibia and metatarsus I, proventral view. Scale lines = 1 mm.

promargin with about 5 large and 6 small and 2 very small teeth, basomesally
with 2 small teeth.

Leg formula 4123. Spination (no spines on tarsi): leg I, femur p3d4r3, patella
pi, tibia p2r2v3 + megaspine, metatarsus plv5; leg II, femur p3d3r3, patella pi,
tibia plrlv4, metatarsus plv8; leg III, femur p3d3r4, patella plrl, tibia p3r3v6,
metatarsus p5r4v8; leg IV, femur p3d4r5, patella pi, tibia p2r3v6, metatarsus
p5dlr3v9. Scopulae: tarsi I, II, thin for distal three quarters; tarsi III scopulate
for distal half, entire; tarsi IV scopulate, divided by setae for distal one-fifth. All
leg tarsi curved, pseudosegmented. Tibia I distally with retrolateral mound
bearing megaspine (Fig. 6), ventral metatarsus I with rounded thumb proximally
with conical process above it on mid-lateral face. Paired tarsal claws with two
rows of teeth, one short distal of about 4 teeth on inner edges, about 7
proximally on outer edges; third claw bare. Trichobothria: 20-30 in slightly
irregular row on tarsi; 30-40 in curving line on metatarsi,; about 11 for half of
tibial length in each of two rows.

THE JOURNAL OF ARACHNOLOGY

III

Palp

Femur

12.85

12.54

11.00

14.05

7.40

Patella

4.95

4.75

4.15

4.63

3.40

Tibia

11.11

10.63

9.86

12.82

6.96

Metatarsus

12.96

13.05

14.15

18.80

—

Tarsus

8.76

9.30

8.35

9.60

2.40

Total

50.63

50.27

47.51

59.90

20.16

Palp (Fig. 8) with long slender tibia,; cymbium short rounded; bulb pyriform
with small subtegulum; embolus broad with scooped tip. Spines, femur pld4rl,
patella 0, tibia p2v2.

Abdomen 13.30 long, 5.35 wide. Three-segmented posterior lateral spinnerets
with basal, median, apical segments 6.83, 7.33, 12.83 long, respectively. Posterior
median spinnerets 2.56 long, 0.24 wide, 0.96 apart.

Paratype female: (Figs. 9-11). Total length, including chelicerae, 43. Carapace
orange brown with brown mottling on caput and interstrial ridges; chelicerae and
legs red brown. Dorsum of abdomen brown with medial pallid area, venter
brown.

Carapace 13.17 long, 12.33 wide; with golden brown hairs forming bush on
lateral margins and along strial edges; setation less dense centrally. Foveal bristles
absent. Fovea short recurved open; clypeus narrow, distinct; caput low; striae
deep, distinct; seven thick bristles on clypeal edge.

Eight eyes on tubercle occupying about 0.39 of front width. Ratio of eyes,
anterior lateral: anterior median: posterior lateral: posterior median, 18:15:16:12.
Anterior row straight; medians separated by 0.6 of their diameter, 0.2 from
laterals. Posterior row recurved, medians separated by twice their diameter, 0.1
from laterals. Median ocular quadrangle wider than long (47/25), narrower in
front (35/47). Lateral eyes of each side separated by 0.2 of AME diameter.

Sternum 6.08 long, 5.60 wide; length of posterior, 1.00, middle, 0.64, sigilla,
respectively, all oval to sub-oval, marginal. Labium 1.92 long, 2.40 wide, with no
cuspules. Palpal coxae 5.04 long behind, 4.24 long in front, 2.40 wide, with about
60 cuspules (not on mound) on inner angle; anterior lobe indistinct with well-
developed serrula. Chelicerae short, rounded, geniculate, with long brown bristles
between golden brown pile; promargin with about 5 large and 7 smaller teeth,
basomesally with 30-40 granules and 7 small teeth.

Leg formula 4123. Numerous bushy hairs on pro- and retrolateral femora;
peacock blue hairs on all femora, patellae, and tibiae. Spination (no spines on
tarsi): leg I, femur p3d2rl, patella pi, tibia p2v4, metatarsus v6,; leg II, femur
p4d3rl, patella pi, tibia p2v4, metatarsus plv7; leg III, femur p3d3r3, patella
plrl, tibia p2r2v6, metatarsus p5r3v8; leg IV, femur p3d3r4, patella plrl, tibia
p2rlv6, metatarsus p5r5v8. Scopulae: tarsus I, thin for full length, divided by two
almost straight lines of setae; tarsus II, as for I but distally setal lines becoming
irregular forming about 4 rows; tarsus III and IV, as for II, but divided by 2-3
rows on III, and by 8-10 rows of setae with scopula reduced to two narrow bands
on IV. Scopula hairs with longitudinal grooves with common herring-bone
corrugations (Fig. 4); few fimbriations present. All tarsi pseudosegmented (Figs.
1, 2), with transverse fissures almost circling segment; ventrally fissures divide
forming separate diamond-shaped plates. Paired tarsal claws with two rows, one
short distal of about 4 teeth on inner edges, about 7 proximally on outer edges;

PAZ & RAVEN— A NEW SPECIES OF LINOTHELE

Figures 7, 8. — Linothele megatheloides , holotype male: 7, holotype male, abdomen and spinnerets,
ventral view; 8, palpal tibia, cymbium and bulb, retrolateral view. Scale lines = 1 mm.

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Figures 9-12. — Linothele megatheloides: 9-11, female paratype; 9, carapace, chelicerae, abdomen,
and spinnerets, dorsal view; 10, sternum, maxillae, labium, and chelicerae, ventral view; 11,
spermathecae, ventral view; 12, holotype male, sternum, maxillae, labium, and chelicerae, ventral
view. All scale lines = 1 mm.

PAZ & RAVEN— A NEW SPECIES OF LINOTHELE

third claw bare. Trichobothria similar to male; base of bothrium with shallow
indistinct corrugations near aperture (Fig. 3). Cuticle almost smooth.

III

Palp

Femur

13.94

14.15

12.76

16.35

9.01

Patella

6.95

6.10

5.50

6.00

4.98

Tibia

12.50

11.35

10.45

13.62

7.76

Metatarsus

11.90

12.10

13.24

17.78

—

Tarsus

7.05

7.17

7.40

8.80

6.91

Total

52.34

50.87

49.35

62.55

28.66

Palpal spines, femur pld4rl, patella p3, tibia p2v6, tarsus v2. Claw with six
very short teeth on short diagonal row.

Abdomen 22.17 long, 12.50 wide. Three-segmented posterior lateral spinnerets
with basal, median, and apical segments 7.83, 7.50, 15.00 long, respectively.
Posterior median spinnerets represented only by scars. Spermathecae two, each
with long lobe apically enlarged with a shallow apical invagination.

Material Examined. — The holotype plus 1 male, 2 females, 2 penultimate
males, between kilometers 178-134, via Quibdo, Medellin, at an altitude of 85 m,
N. Paz S., 20 Feb. 1983, deposited in the American Museum of Natural History,
New York.

Remarks. — The pseudosegmented tarsi (Figs. 1, 2; see Raven 1985 for
explanation of wider occurrence) are extremely flexible. They are considered the
most apomorphic state of leg tarsi in mygalomorphs; other states being cracked
tarsi (usually only one or few transverse fissures), pallid cuticle that is indicative
of a weakness, and normal tarsi. In L. megatheloides , closer study of the
pseudosegmentation (Fig. 2) shows that the “cracking clay” affect may be quite
regular laterally.

Associated with the pseudosegmented tarsi (and diagnostic of the Diplurinae)
are what appear to be scopulae. The hairs resemble a scopula because they are
short, straight, erect, and on the ventral surface of the tarsi. The hairs show the
same canaliculi or fluting as that seen on the leg setae (dorsal) and spines of
many mygalomorphs, and have very few fimbriations which would increase
surface area. In contrast, leg scopulae of theraphosids are dense pads of highly
fimbriated setae. It is thus likely that the term “scopula” needs to be redefined.
Further study is needed to test the hypothesis that the leg scopulae of the
Crassitarsae (Raven 1985) are homologous.

In most Tuberculotae, the bothrial bases are corrugiform. In some cases, the
corrugations cover the base (e.g., the six-eyed diplurid Masteria ; Raven 1979, fig.
21). However, in Linothele megatheloides , the corrugations are very shallow and
confined to the upper portion of the base.

ACKNOWLEDGMENTS

We are grateful to B. Mitchell for drawing the excellent figures and to the
Australian Research Council for a grant to RJR.

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LITERATURE CITED

Coyle, F. A. 1986. The role of silk in prey capture by nonaraneomorph spiders. Pp. 269-305, In
Spiders: Webs, Behavior, and Evolution. (W. A. Shear, ed.). Stanford University Press, Stanford.

Paz S., N. 1988. Ecologia y aspectos del comportamiento en Linothele sp. (Araneae, Dipluridae). J.
Arachnol. 16:5-22.

Raven, R. J. 1979. Systematics of the mygalomorph spider genus Masteria (Masteriinae: Dipluridae:
Arachnida). Aust. J. Zool., 27: 623-636.

Raven, R. J. 1985. The spider infraorder Mygalomorphae (Araneae): cladistics and systematics. Bull.
Amer. Mus. Nat. Hist., 182:1-180.

Strand, E. 1908. Diagnosen neuer aussereuropaischer Spinnen. Zool. Anz., 32:769-773.

Manuscript received May 1989, revised July 1989.

Cushing, R E. and B. D. Opell. 1990. The effect of time and temperature on disturbance behaviors

shown by the orb-weaving spider Uloborus glomosus (Uloboridae). J. Arachnol., 18:87-93.

THE EFFECT OF TIME AND TEMPERATURE ON
DISTURBANCE BEHAVIORS SHOWN BY THE ORB-WEAVING
SPIDER ULOBORUS GLOMOSUS (ULOBORIDAE)

Paula E. Cushing and Brent D. Opell

Department of Biology

Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061 USA

ABSTRACT

When disturbed, Uloborus glomosus either remain in position at the hub of their orb-webs, jump
from the web, move to the edge of the web, or shake the web. The time of day influences which of
these behaviors is expressed. Spiders tend to jump in the afternoon and the evening but not in the
morning. In the morning they tend to move to the edge of the web or remain in position. The
tendency to shake the web is approximately the same throughout the day. Ambient temperature
appears not to be the principal factor explaining the differences in jumping, moving to the edge, and
remaining in position. Historical differences in the activity patterns of various spider predators may
have influenced the time-related expression of disturbance behavioral patterns.

INTRODUCTION

Many orb-weaving spiders show predictable responses when disturbed. Some
run to a retreat or to surrounding vegetation, others move to the edge of the web,
others shake the web and others jump from the web (Pekham and Pekham 1887;
Levi 1968; Marples 1969; Eberhard 1970, 1973; Robinson and Robinson 1970;
Robinson 1978; Ewer 1972; Edmunds 1974; Tolbert 1975;, Levi 1977; Hoffmaster
1982; Cushing and Opell in press). These behaviors are thought to be predator
avoidance strategies. The jumping and shaking responses have been cited as
responses to a variety of predators including both spider-hunting wasps and
salticid spiders (Richards and Hamm 1939; Eberhard 1970; Coville 1976;
Hoffmaster 1982; Cushing and Opell in press).

When the spider Uloborus glomosus (Walckenaer) (Uloboridae) is disturbed
while resting beneath the hub of its horizontal orb-web, it may show one of four
responses: jumping from the web, shaking the web, moving to the edge of the
web, or remaining in position (Cushing and Opell in press). Many factors,
including time of day, evidently influence the expression of the behaviors. The
objectives of this study are to determine how time of day influences the
disturbance behaviors shown by these spiders and if temperature mediates these
behavioral patterns.

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METHODS

Forty-nine adult female Ulohorus glomosus were collected from shrubbery at
various locations on the V. P. I. and S. U. campus (Blacksburg). When collected
no spiders had eggsacs, although many subsequently produced eggsacs, a factor
not considered in the analyses. Twenty-five spiders were collected in mid-July,
1987 and assigned to Group I. Others collected in late July were in Group II. All
spiders were maintained in an outdoor study enclosure in a wooded area of
Blacksburg.

Spiders in Group I were marked for identification by applying small dots of
green and red enamel paint to their dorsal abdominal surfaces. The dots were
observed by holding a long-handled dental mirror beneath a spider on its orb
web. Group I spiders were established on six frames, each providing a vertical
series of 25 wooden dowel rods spaced 12 cm apart. Each rod was 8 mm in
diameter and 50 cm long. Spiders chose their own web attachment sites and were
maintained at a density of one to four spiders per frame. Frames were kept in a 3
X 3 X 3 m screened enclosure to prevent dispersal away from the study area.
Group II spiders were kept in 31 X 16.5 X 9 cm plastic shoeboxes covered with
mosquito netting and placed under a plastic roof just outside the screened
enclosure housing Group I spiders. We began testing Group I on 13 July, and
Group II 7 days later. Group I spiders were removed and the experiment
terminated after 19 days of testing. Group II spiders were tested for 36 days.

As a disturbance stimulus we dropped water on the venter of each spider from
a Pasteur pipette with an average tip diameter of 1.20 mm held 1 cm above the
spider. The water was kept in the enclosure to maintain it at ambient
temperature. This stimulus was suggested by W. G. Eberhard (pers. comm.) as it
is more easily standardized than touching the spider with a probe. A water drop
was considered to approximate the sudden ventral contact by an attacking
predator such as a wasp or a hunting spider. Since U. glomosus does not respond
to the visual or vibratory stimuli produced by a tethered wasp held directly above
the spider (Cushing and Opell in press), visual and vibratory stimuli were
considered inappropriate disturbance stimuli. After stimulating a spider, we
recorded its response to this disturbance as either: jumping out of the web,
moving to the edge of the web, remaining in position, or shaking the web.
Preliminary observations showed that the spiders responded similarly to a water
drop as to contact by a small probe.

Temperature was recorded at the time observations were begun. It took
approximately 30 minutes to test all of the spiders’ responses. For both groups,
we tested all spiders in the morning (0800-1000 hours) of day 1 of the tests and
recorded their behaviors. On day 2, we tested all the spiders in the afternoon
(1200-1400 hours) and on day 3 we tested them in the evening (1600-1800 hours).
These times corresponded to the times used by Cushing and Opell (in press).
Spiders were not disturbed on day 4 to ensure 24 hours between tests. This 24
hour testing sequence was a cautionary measure chosen to diminish any
degeneration of the behaviors that might result from too frequently disturbing the
spiders. On day 5, the 3-day cycle, hereafter referred to as a block, was repeated.
Group I spiders were run for 5 blocks (15 days of actual testing) and Group II
spiders for 9 blocks (27 days of actual testing).

CUSHING & OPELL — ULOBORID SPIDER DISTURBANCE BEHAVIORS

Table 1. — The frequencies of each behavior during the morning, afternoon and evening. Total
number of observations is 862. *=Two spiders died before the final evening observations were
recorded.

Response

Time of day

Morning

Afternoon

Evening

Total

Jumped from web

116

172

169

457

Moved to edge

Remained in position

147

Shook web

208

Total

288

286*

862

If a spider died or disappeared before half of the observations were completed,
all the previous observations for that individual were eliminated from the data
set. This ensured that each spider in Group I and in Group II contributed an
approximately equal sequence of observations to the data set. Consequently, a
spider from Group I had to survive through block 3 for its behaviors to be
included in the analyses and one from Group II had to survive through block 5.
Observations for 22 Group I and for 21 Group II spiders were used in the final
analyses.

To supplement their diet of small insects that passed into the enclosure, we fed
all spiders by blowing several fruit flies ( Drosophila sp.) into their webs, either
after testing in the evening of the three-day cycle or on the fourth (non-test) day.
Group II spiders relied solely on this source of food.

To determine the validity of pooling the responses of all 43 spiders, we
conducted a Replicated Goodness-of-Fit Test for heterogeneity (Sokal and Rohlf
1981), comparing the pooled responses of Group I spiders with the pooled
responses of Group II spiders. To determine the effect of the variable Time on the
responses of these spiders, we pooled the observations for each of the behavioral
categories made during each of the three time periods across all 43 spiders for a
total of 882 observations (Table 1). We conducted a log-linear analysis to
determine if the variables Time and Response are associated and, if so, to
establish the patterns of behavioral switching that occurred (Bishop et al. 1975;
Fienberg 1987).

To assess the magnitude of the interactions between each of the three Time
categories with each of the four Response categories, we calculated the ratios of
the log-linear parameter estimates to the standard errors for the log-linear model
with the two-way interaction term between Time and Response. These ratios are
somewhat analogous to cell chi-square values. The greater the ratio term, the
greater the effect of those categories on the association between Time and
Response. As the parameter estimates are calculated according to the assumption
of normality, ratio terms greater than / 1.96/ correspond to a significance level
less than 0.05 in a Z-table and indicate category interactions that contribute most to
the association between Time and Response. Positive ratios indicate a positive
interaction between the categories; negative ratios indicate a negative interaction
(Kennedy 1983).

To determine the effect of Temperature on the behaviors, we conducted a
discriminant analysis, defining Temperature as the independent continuous
variable and Response as the classification variable.

THE JOURNAL OF ARACHNOLOGY

Table 2. Ratio terms (Z-values) for the Time X Response association. * -- P < 0.05.

Response

Time

Morning

Afternoon

Evening

Jumped from web

-5.541*

2.919*

2.333*

Moved to edge

2.233*

-1.290

-0.581

Remained in position

2.107*

-0.867

-0.972

Shook web

-1.023

0.800

0.139

RESULTS

Association between Time and Response. — The test for heterogeneity between
Groups I and II indicated that they were homogeneous (G2 = 1.1078, P > 0.5).
Therefore, we pooled responses for all 43 spiders. Over the entire testing period,
spiders jumped from the web 53% of the time, moved to the edge 6% of the time,
remained in position 17% of the time, and shook the web 24% of the time (Table
1).

The two-way log-linear analysis comparing the interaction between the Time
and Response variables indicated that spider response is influenced by the time of
day (G2 = 34.947, P < 0.001). The magnitudes of the interactions between each
of the Time categories with each of the Response categories is presented in Table
2. In the morning, spiders did not tend to jump from the web in response to the
disturbance but did tend to either move to the edge of the web or remain in
position. Spiders tended to jump from the web in the afternoon and the evening.
They showed no time-related preference for the shaking behavior although
shaking the web was the second most frequent response (Table 1).

Effect of Temperature on the behaviors.— The mean temperature during the
morning tests was 20.2° C (SD = 3.05); the mean during the afternoon tests was
28.2° C (SD — 3.01); and the mean during the evening tests was 26.8° C (SD =
3.07).

To calculate the discriminant function, the within-group covariance matrix
rather than the pooled covariance matrix was used because the within-group
covariance matrix for the Response variable was not homogeneous (x2 = 0.004, P
< 0.05, Kleinbaum and Kupper 1978). According to the discriminant analysis,
temperature is not a good predictor of the disturbance behaviors (Table 3).

DISCUSSION

This study supports Cushing and Opell’s (in press) finding that Uloborus
glomosus responds differently to disturbance at different times of the day. It also
indicates that ambient temperature may not be the principal factor explaining
these differences. Temperature correctly predicted whether a spider moved, shook,
or remained in position less than 42% of the time; the jumping response was
correctly predicted 66% of the time. The jumping response appears to be an
energetically expensive behavior (Cushing and Opell in press) and, therefore, may
be enhanced by higher temperatures.

Jumping from the web is effective against aerial hunters such as spider-hunting
wasps and hummingbirds (Eberhard 1970; Coville 1976; Hoffmaster 1982;

CUSHING & OPELL — ULOBORID SPIDER DISTURBANCE BEHAVIORS

Table 3. — Observations (Total 862) correctly and incorrectly assigned by a discriminant analysis to
each of the Response categories using Temperature as a predictor.

% Incorrectly assigned to:
% Correctly — “ ” — - - -

Response

Freq.

assigned

Jumped

Moved

Remained

Shook

Jumped from web

457

66.1

—

1.8

19.9

12.3

Moved to edge
Remained in

12.0

40.0

—

42.0

6.1

position

147

41.5

28.6

13.6

—

16.3

Shook web

208

17.3

45.7

1.9

35.1

—

Cushing and Opel! in press). Wasps are not very successful at stinging spiders
hanging on threads beneath orb-webs and rarely pursue spiders after they have
jumped unless they have landed on a solid substrate (Eberhard 1970). The same is
probably true for hummingbirds, one of the more important avian predators of
spiders. These birds supplement their nectar diet with protein from spiders
(including orb-weavers) and insects (Pyke 1980; Johnsgard 1983).

Jumping behavior does not appear to be effective against ambulatory predators
such as salticid spiders. Robinson and Valerio (1977) noted that araneids that
jumped from their webs after being attacked by salticids could not displace the
jumping spider. When a spider jumps from its web, it also risks losing a
productive web site if its dragline breaks or becomes entangled in surrounding
vegetation, falling into the web of a neighboring spider, or becoming prey of an
ambulatory predator on the substrate to which it falls. Therefore, if the stimulus
is not immediately threatening an alternate avoidance strategy such as shaking the
web may be advantageous. This behavior may dislodge an ambulatory predator
(i.e., a salticid spider) from both the orb-spider and the web plane (Robinson and
Valerio 1977; Hoffmaster 1982).

If it is true that jumping from the web is most effective against aerial predators
and shaking the web against ambulatory predators, then the expression of these
behaviors at particular times of day may have been selected by differences in the
activity patterns of these predators. Hummingbirds are primarily nectar feeders.
Nectar flows most abundantly from one to two hours before hummingbirds
become active (about 0430 hours) until around 1830 hours when hummingbirds
cease activity (Cruden et al. 1983). Hummingbirds tend to hunt insects and
spiders only casually in the morning, spending most of their time feeding on
nectar. They more actively hunt arthropods as the day progresses (after nectar
production has dropped off) (Stiles and Wolf 1979; Gill pers. comm.).

Adult spider-hunting wasps of the families Sphecidae and Pompilidae are also
primarily nectar feeders only occasionally eating the spiders they hunt (Evans and
Eberhard 1970). Coville (1987) states that these wasps are active from one to
three hours after sunrise to one to three hours before sunset. Although their daily
activity cycles have not been described, it is probable that they also spend the
early morning hours foraging for nectar. They seem to build their nests and hunt
for spiders most actively between 1100 hours and 1830 hours (Bristowe 1948;
Cushing 1988).

The activity patterns of these aerial predators may explain the tendency of U.
glomosus to jump in the afternoon (1200-1400 hours) and the evening (1600-1800

THE JOURNAL OF ARACHNOLOGY

hours) but not in the morning (0800-1000 hours). If this explanation is correct,
the jumping response should be as infrequent late in the day (i.e., from 1800-2000
hours) as in the morning. Spiders that jump in the afternoon and the evening but
not in the morning must switch to some other behavior in the early hours. This
study suggests that these spiders move to the edge of the web or remain in
position when disturbed. Both of these behaviors are energetically and
strategically inexpensive, but probably not very effective if the stimulus is an
actual ambulatory (or aerial) predator.

Shaking behavior is the second most frequent behavior and occurs at equal
frequency regardless of time of day or temperature. This may also be related to
the activity pattern of the main predator group to which it is directed, namely
ambulatory predators. Salticid spiders are an important ambulatory predator of
orb-weaving spiders, especially in the tropics (Bristowe 1941; Enders 1974, 1975;
Robinson and Valerio 1977; Edwards pers. comm.). Their activity patterns have
been described as beginning as early as 0700 hours and ending as late as 1900
hours (Anderson 1970; Abraham 1983), although Gardner (1965) and Edwards
(pers. comm.) have observed salticids hunting most actively between 1000 hours
and 1600 hours. Because these ambulatory predators are active throughout the
day, the shaking behavior should also be shown throughout the day, as this study
shows it to be.

ACKNOWLEDGMENTS

We thank Richard D. Fell, Thomas A. Jenssen, and David A. West for their
advice and input. James E. Carrel and an anonymous reviewer provided helpful
comments on the manuscript. The Statistics Consulting Center of V. P. I. and S.
U. provided advice on experimental design and the interpretation of the analyses.
This project was supported by two grants from Sigma Xi and matching funds
from the Department of Biology of V. P. I. and S. U.

LITERATURE CITED

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(Arachnida: Araneae). J. Arachnol., 11:31-50.

Anderson, J. F. 1970. Metabolic rates of spiders. Comp. Biochem. Physiol., 33:51-72.

Bristowe, W. S. 1941. The Comity of Spiders, vol. 2. Ray Soc. No. 128, London.

Bristowe, W. S. 1948. Notes on the habits and prey of twenty species of British hunting wasps. Proc.
Linn. Soc. Lond., 160:12-37.

Bishop, Y. M. M., S. E. Fienberg and P. W. Holland. 1975. Discrete Multivariate Analysis: Theory
and Practice. M. I. T. Press, Cambridge.

Coville, R. E. 1976. Predatory behavior of the spider wasp, Chalybion calif ornicum (Hymenoptera:
Sphecidae). Pan-Pac. Ent., 52:229-233.

Coville, R. E. 1987. Spider hunting sphecid wasps. Pp. 309-318, In Ecophysiology of Spiders (ed. W.

Nentwig). Springer- Verlag, Berlin.

Cruden, R. W., S. M. Hermann and S. Peterson. 1983. Patterns of nectar production and plant-
pollinator coevolution. Pp. 80-125, In The Biology of Nectaries. (B. Bentley and T. Elias, eds.).
Columbia Univ. Press, New York.

Cushing, P. E. 1988. A study of disturbance behaviors in Uloborus glomosus (Araneae; Uloboridae) as
possible predator avoidance strategies. M. S. thesis, Virginia Polytechnic Institute and State
University, Blacksburg, Virginia.

CUSHING & OPELL — ULOBORID SPIDER DISTURBANCE BEHAVIORS

Cushing, P. E. and B. D. Opelh In Press. Disturbance behaviors in the spider Uloborus glomosus
(Araneae, Uloboridae): Possible predator avoidance strategies. Can. J. Zool.

Eberhard, W. G. 1970. The predatory behavior of two wasps, Agenoideus humilis (Pompilidae) and
Sceliphron caementarium (Sphecidae), on the orb weaving spider Araneus cornutus (Araneidae).
Psyche, 77:243-251.

Eberhard, W. G. 1973. Stabilimenta on the webs of Uloborus diversus (Araneae: Uloboridae) and
other spiders. J. Zool. Lond., 171:367-384.

Edmunds, M. 1974. Defense in Animals: A Survey of Antipredator Defences. Longmans, Essex.

Enders, F. 1974. Vertical Stratification in orb-web spiders (Araneidae, Araneae) and a consideration of
other methods of coexistence. Ecology, 55:317-328.

Enders, F. 1975. The influence of hunting manner on prey size, particularly in spiders with long attack
distances (Araneidae, Linyphiidae, and Salticidae). Amer. Natur., 109:737-763.

Evans, H. E. and M. J. W. Eberhard. 1970. The Wasps. Univ. of Michigan Press, Ann Arbor,
Michigan.

Ewer, R. F. 1972. The devices in the web of the West African spider Argiope flavipalpis. J. Nat. Hist.,
6:159-167.

Fienberg, S. E. 1987. The Analysis of Cross-Classified Categorical Data, 2d ed. M. I. T. Press,
Cambridge.

Gardner, B. T. 1965. Observations on three species of Phidippus jumping spiders (Araneae:
Salticidae). Psyche, 72:133-147.

Hoffmaster, D. K. 1982. Predator avoidance behaviors of five species of Panamanian orb-weaving
spiders (Araneae; Araneidae, Uloboridae). J. Arachnol., 10:69-73.

Johnsgard, P. A. 1983. The Hummingbirds of North America. Smithsonian Institution Press,
Washington, D. C.

Kennedy, J. J. 1983. Analyzing Qualitative Data: Introductory Log-Linear Analysis for Behavioral
Research. Praeger Scientific, New York.

Kleinbaum, D. G. and L. L. Kupper. 1978. Applied Regression Analysis and Other Multivariable
Methods. Duxbury Press, Boston.

Levi, H. W. 1968. The spider genera Gea and Argiope in America (Araneae: Araneidae). Bull. Mus.
Comp. Zool., 136:319-352.

Levi, H. W. 1977. The American orb-weaver genera Cyclosa, Metazygia and Eustala north of Mexico
(Araneae: Araneidae). Bull. Mus. Comp. Zool., 148:61-127.

Marples, B. J. 1969. Observations on decorated webs. Bull. Br. Arachnol. Soc., 1:13-18.

Pekham, G. W. and E. G. Pekham. 1887. Some observations on the mental powers of spiders. J.
Morph., 1:383-419.

Pyke, G. H. 1980. The foraging behaviour of Australian honeyeaters: a review and some comparisons
with hummingbirds. Aust. J. EcoL, 5:343-369.

Richards, O. W. and A. H. Hamm. 1939. The biology of the British Pompilidae. Trans. Soc. Brit.
Ent., 6:51-114.

Robinson, M. H. 1978. Developmental studies of Argiope argentata (Fabricius) and Argiope aemula
(Walckenaer). Symp. Zool. Soc. Lond., 42:31-41.

Robinson, M. H. and B. Robinson. 1970. The stabilimentum of the orb web spider Argiope argentata:
an improbable defense against predators. Can. Entomol, 102:641-655.

Robinson, M. H. and C. E. Valerio. 1977. Attacks on large or heavily defended prey by tropical
salticid spiders. Psyche, 84:1-10.

Sokal, R. R. and F. J. Rohlf. 1981. Biometry. W. H. Freeman, San Francisco.

Stiles, F. G. and L. L. Wolf. 1979. Ecology and evolution of lek mating behavior in the long-tailed
hermit hummingbird. Ornith. Monogr. 27:1-78.

Tolbert, W. W. 1975. Predator avoidance behaviors and web defensive structures in the orb weavers
Argiope aurantia and Argiope trifasciata (Araneae, Araneidae). Psyche, 82:29-51.

Manuscript received June 1989, revised July 1989.

Coyle, F. A. and T. E. Meigs. 1990. Two new species of Ishnothele funnelweb spiders (Araneae,
Mygalomorphae, Dipluridae) from Jamaica. J. Arachnol., 18:95-111.

TWO NEW SPECIES OF ISCHNOTHELE FUNNELWEB
SPIDERS (ARANEAE, MYGALOMORPHAE, DIPLURIDAE)

FROM JAMAICA

Frederick A. Coyle and Thomas E. Meigs

Department of Biology
Western Carolina University
Cullowhee, NC 28723 USA

ABSTRACT

Based upon an analysis of patterns of variation in morphology, pigmentation, habitat, and
Mysmenopsis kleptoparasites, two new species of Ischnothele from Jamaica (/. reggae and I. xera ) are
described. These allopatric sister species appear to have cospeciated with their respective Mysmenopsis
kleptoparasite species, also each other’s closest relatives. The rate of divergent evolution of the two
kleptoparasite populations appears to be greater than that of the host populations, in part, we suggest,
because of the kleptoparasites’ shorter generation time.

INTRODUCTION

This study is part of the first author’s revisionary study of the ischnotheline
funnelweb spiders, tropical diplurids with two rows of cheliceral teeth, an
elongate terminal cymbial apophysis, and maxillary (but not labial) cuspules. The
genus Ischnothele (Figs. 1, 2) is distributed throughout much of the American
tropics and differs from the other two (Old World) ischnotheline genera
( Thelechoris and Lathrothele) by the presence of spines on the male tibia I
apophysis (Figs. 12-17), by the presence of an opposing protuberance on the male
metatarsus I (Figs. 12-17), and by a reasonably clear demarcation between the
bulb and embolus (Figs. 22, 23).

The unpublished occurrence of Ischnothele on Jamaica came to light during an
examination of museum collections and prompted the first author to make a
four-day visit to that island in early April of 1988 during a collecting trip to the
American tropics. Collecting in Jamaica was limited to several areas in the
southeastern part of the island (the source of 95% of previously collected
specimens) and revealed marked geographic variation in the habitat,
kleptoparasites, pigmentation, and morphology of these Ischnothele populations.
Although more careful searching in this and other parts of Jamaica for additional
and larger population samples will be needed to rigorously test hypotheses about
Ischnothele species limits, we believe that we currently have sufficient data to
postulate that there are two species of Ischnothele on Jamaica, and we hope that
the presentation of such information will stimulate and guide future research.
Moreover, our findings provide the first clear evidence for the kind of host-
kleptoparasite cospeciation process which may be a key factor in the evolution of

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Figures 1, 2. — Ischnothele reggae paratype, female body; 1, dorsal, showing abdominal
pigmentation and bristles on chelicerae and carapace; 2, lateral.

the mysmenid genus Mysmenopsis (Platnick and Shadab 1978; Coyle and Meigs
1989), many species of which are kleptoparasites of diplurid spiders.

These two species of Ischnothele are endemic to Jamaica and are clearly each
other’s closest relatives. Of the several probable synapomorphies linking these
species, two are especially distinctive: (1) spermathecae short and stalkless (or
with a very short, broad vestigial stalk), and (2) embolus serrated. Two
synapormorphies support the hypothesis that this species pair is most closely
related to endemic species from Cuba (Ischnothele longicauda Franganillo) and
Hispaniola: (1) ventral surface of male metatarsus I with distal keel, and (2)
embolus short. A more complete phylogenetic analysis of all ischnotheline taxa
will be presented in the forthcoming revision.

METHODS

The quantitative characters used in this study are abbreviated and defined as
follows: MC, number of cuspules on ventral surface of maxilla; ITSP and ITSR,
number of spines on prolateral and retrolateral surfaces of male tarsus I,
respectively; TAS, number of spines on male tibial mating apophysis; CSP and
CSR, number of enciform spines on prolateral and retrolateral surfaces of male
cymbial apophysis, respectively; CTP and CTR, number of cheliceral teeth in
prolateral and retrolateral rows, respectively; CDP and CDR, number of

COYLE & MEIGS— TWO NEW ISHNOTHELE SPECIES FROM JAMAICA

Figures 3-6. — Photos of living specimens of Jamaican Ischnothele species, dorsal view; 3, 4, /.
reggae; 3, male holotype; 4, female paratype; 5, 6, /. xera; 5, male holotype; 6, female paratype. Scale
bar = 5 mm.

cheliceral denticles adjacent to prolateral and retrolateral rows of teeth,
respectively; PTarS, number of spines on female palpal tarsus; ITarS, number of
spines on female tarsus I; CS, length of longest seta protruding from male
carapace edge above coxa III; CL, carapace length; CW, carapace width; AMD,
transverse diameter of left anterior median eye pupil; AMS, minimum distance

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Burnt Hill

Figure 7. — Distribution of Jamaican Ischnothele species. Triangles designate collection localities for
I. reggae , circles for I. xera , X’s for juveniles only. Black bars designate areas where first author
searched unsuccessfully for Ischnothele. Dotted line encloses area receiving over 75 inches of rainfall
per year.

between anterior median eye pupils; OQW, ocular quadrangle width; SL, sternum
length; SW, sternum width; IFL, ITL, IML, and ITarL, lengths of leg I femur,
tibia, metatarsus, and tarsus, respectively; ITT, maximum diameter of male tibia I
in retrolateral view along line perpendicular to ITL; MKP, distance along IML
line from proximal end of male metatarsus I to the intersection with
perpendicular line passing through the prolateral keel apex; TAL, distance from
disto-dorsal angle of male tibia I apophysis to base of apophysis in retrolateral
view (Fig. 15); TAW, midpoint diameter of male tibia I apophysis in retrolateral
view (Fig. 15); PFL and PTL, lengths of male palpal femur and tibia,
respectively; PTT, maximum diameter of male palpal tibia in retrolateral view
along line perpendicular to PTL; CYL, length of male cymbium (including
apophysis) in prolateral view; CYAL, length of male cymbial apophysis from
apex of prolateral cymbial lobe to tip of apophysis along line parallel to CYL;
PL, distance from tip of embolus to most distant edge of palpal bulb (Fig. 23);
PD, maximum diameter of palpal bulb (Fig. 23); ML, distance from proximal-
most maxillary cuspule to tip of endite along line parallel to longitudinal axis of
maxilla with ventral surface of maxilla in horizontal plane; CFL, distance along
ML from proximal-most cuspule to perpendicular line that intersects distal-most
cuspule; LSL1, LSL2, and LSL3, lengths of posterior lateral spinneret articles
(basal, middle, and terminal article, respectively) measured along midventral line.

All appendage character states were recorded from the left appendage (unless
missing, damaged, or not fully regenerated) except for ITSP, ITSR, TAS, CSP,
and CSR, which were recorded from both appendages. All carapace and eye
measurements were performed in dorsal view with the lateral borders of the
carapace in the horizontal plane. The length of each leg article and of the palpal
femur and tibia was measured in retrolateral view and equals the distance from

COYLE & MEIGS— TWO NEW ISHNOTHELE SPECIES FROM JAMAICA

Upland

Lowland (E. Kingston)

Lowland (W. Kingston)

□ZED

rrrrT-rT-i

1 4 7

Light — » Dark

DORSAL ABDOMINAL PIGMENTATION

9 TAL

LSL3

Figure 8.— Frequency distribution histogram of abdominal color variation in Jamaican Ischnothele
species. Females designated by open squares, males by crossed squares. Figures 9-11. — Scattergrams
for /. reggae (triangles) and L x era (circles) with regression lines (values in mm); 9, males, TAW vs.
TAL (/. xera regression: y = 0.105x + 0.139); 10, males (open symbols) and females (closed symbols),
OQW vs. CL (/. reggae regression: y = 0.212x + 0.253; I. xera regression: y = 0.188x + 0.214); 11,
females, OQW vs. LSL3 (/. reggae regression: y = 0.142x + 0.678; I. xera regression: y = 0.1 18x X +
0.446)

the proximal point of articulation to the most distodorsal point of the article (in
the case of IFL the distal point of measurement is the tip of the condyle, which is
sometimes slightly proximal of the most distal point of the article). PL and PD
were recorded after positioning the palpal organ for a retrolateral and slightly
ventral view with the bulb and embolus tip in the same horizontal plane.

Measurements were performed with a Wild M-5® stereomicroscope with 20X
eyepiece lenses and an eyepiece micrometer scale. LSL1, LSL2, and LSL3
measurements are accurate to 0.076 mm; SL (females), SW (females), ML, CFL,
PFL, PTL, PTT, CYL, CYAL, PL, and PD are accurate to 0.018 mm; AMD,
AMS, OQW, TAL, and TAW are accurate to 0.009 mm; all other measurements
are accurate to 0.038 mm. All measurements are in millimeters.

Spermathecae were cleared in 85% lactic acid, viewed at 100-400X through a
compound light microscope, and drawn with the aid of a drawing tube.

100

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Table 1. — Quantitative character values for Jamaican Ischnothele males. Character abbreviations
are defined in the Methods section of the text. All measurements given in millimeters. Range and
mean given. ITSP, ITSR, TAS, CSP, and CSR values include data from both left and right
appendages.

reggae
(N= 2)

xera

(N= 3)

reggae

holotype

xera

holotype

51,67

39-52(44.0)

ITSP

0-1(0. 3)

2-4(3. 0)

0,0

3,3

ITSR

0-2(1. 3)

2(2.0)

1,0

2,2

TAS

7-9(8. 5)

4-7(5. 8)

9,7

4,4

CSP

0(0)

0-1 (0.7)

0,0

1,1

CSR

0(0)

0-1(0. 7)

0,0

1,1

3.66,3.73

3.54-4.20(3.97)

3.73

4.16

3.31,3.43

3.16-3.73(3.53)

3.43

3.70

AMD

0.19,0.20

0.17-0.19(0.182)

0.20

0.19

AMS

0.14,0.17

0.12-0.15(0.133)

0.14

0.12

OQW

1.06,1.06

0.87-1.04(0.974)

1.06

1.04

2.04,2.08

1.89-2.31(2.17)

2.08

2.31

1.58,1.73

1.54-1.96(1.81)

1.73

1.92

IFL

3.35,3.47

3.16-3.70(3.52)

3.35

3.70

ITL

2.73,2.73

2.46-2.93(2.75)

2.73

2.85

ITT

0.69,0.73

0.62-0.85(0.74)

0.73

0.85

IML

2.70,2.73

2.66-3.04(2.88)

2.73

2.93

MKP

1.08,1.08

0.92-1.16(1.07)

1.08

1.12

ITarL

2.54,2.54

2.16-2.89(2.61)

2.54

2.77

TAL

0.11,0.12

0.26-0.41(0.352)

0.12

0.41

TAW

0.23,0.27

0.17-0.19(0.176)

0.23

0.19

PFL

2.17,2.22

2.07-2.48(2.33)

2.17

2.48

PTL

1.63,1.65

1.48-1.74(1.64)

1.63

1.70

PTT

0.67,0.69

0.57-0.70(0.65)

0.67

0.70

CYL

1.48,1.55

1.44-1.85(1.67)

1.55

1.72

CYAL

0.81,0.94

0.83-1.11(1.01)

0.94

1.07

0.83,0.85

0.76-0.89(0.84)

0.83

0.87

0.48,0.48

0.46-0.52(0.49)

0.48

LSL3

3.47,3.47

3.70-3.85(3.77)

3.47

3.77

TAW(100)/TAL

193,243

45-64(51.7)

193

MKP(100)/IML

39,40

35-38(37.0)

OQW(100)/CL

28,29

24-25(24.6)

CS(100)/CW

14,15

18-22(20.6)

Each species description is a composite of all the adult specimens examined;
these sample sizes are given in Tables 1 and 2. The quantitative character values
recorded in these tables are an integral part of each description. Colors are
described from specimens under alcohol, illuminated by a tungsten bulb, and
viewed through a stereomicroscope.

For the analysis of variation of dorsal abdominal pigmentation, three of the
preserved adult specimens in good condition were carefully selected to serve as
standards: one with a relatively dark abdomen, one with a relatively light
abdomen, and one with pigmentation intermediate between these two. These
dorsal abdominal pigmentation values are the result of the distribution of two
components: 1) pigments beneath the abdominal cuticle and 2) light and dark
setae. The three standards were placed side by side in order of increasing

COYLE & MEIGS— TWO NEW ISHNOTHELE SPECIES FROM JAMAICA

101

Table 2. — Quantitative character values for Jamaican Ischnothele females. Character abbreviations
are defined in the Methods section of the text. All measurements given in millimeters. Range, mean,
and standard deviation given.

reggae
(N = 23-27)

xera

(N= 6-8)

CTP

6-12(8.8 ± 1.5)

8-10(9.3 ±0.7)

CDP

0-3(0. 6 ± 0.8)

0-4(0. 9 ± 1.4)

CTR

9-12(10.0 ±0.9)

7-9(8. 4 ± 0.7)

CDR

8-18(13.1 ±2.9)

10-16(13.8 ±2.5)

PTarS

6-16(10.8 ±2.2)

9-13(10.9 ± 1.6)

ITarS

2-7(4. 3 ± 1.0)

5-11(6.3 ±2.1)

72-136(99.7 ± 18.7)

44-91(63.4 ± 18.6)

4.14-7.49(5.45 + 0.82)

3.12-5.97(4.86 ± 1.02)

3.53-6.42(4.78 ± 0.69)

2.74-5.13(4.14 ±0.85)

AMD

0.18-0.31(0.230 + 0.032)

0.13-0.22(0.185 ±0.031)

AMS

0.13-0.24(0.165 ±0.029)

0.09-0.18(0.145 ±0.034)

OQW

1.13-1.83(1.413 ±0.179)

0.80-1.35(1.123 ±0.200)

2.15-3.80(2.87 ±0.39)

1.72-3.05(2.58 ±0.50)

1.93-3.39(2.51 ±0.32)

1.46-2.59(2.20 ±0.40)

1.24-2.26(1.65 ±0.26)

0.89-1.66(1.38 ±0.30)

CFL

0.47-1.24(0.78 ±0.19)

0.35-0.91(0.61 ±0.19)

IFL

3.23-5.74(4.17 ±0.59)

2.32-4.26(3.55 ± 0.72)

ITL

2.28-4.03(2.93 ±0.41)

1.60-3.08(2.52 ±0.54)

IML

2.39-4.10(3.03 ±0.42)

1.75-3.27(2.69 ±0.57)

ITarL

1.48-2.36(1.87 ±0.23)

1.10-2.01(1.65 ±0.33)

LSL1

1.44-2.96(2.06 ±0.32)

1.60-2.36(1.98 ±0.25)

LSL2

1.29-2.89(1.84 ±0.32)

1.37-2.28(1.90 ±0.30)

LSL3

3.95-8.13(5.44 ± 1.08)

3.72-6.69(5.90 ± 1.12)

OQW(100)/CL

24-27(25.9 ± 0.9)

21-26(23.3 ± 1.3)

LSL3(100)/CL

81=1 1 1(97.3 ± 8.8)

101-132(1 18.6 ± 12.8)

QQW(IQ0)/LSL3

23-32(27.1 ±2.9)

18-24(19.6 ±2.4)

AMD(IOO)/ ITarS

3.5-9.6(5.7± 1.3)

1.9-3.8(3.1 ±0.7)

ITarS(100)/CTR

17-67(43.4 ± 10.5)

56-157(76.6 ±33.5)

darkness in an open petri dish of ethanol, which was illuminated by a 6 volt, 15
watt, Olympus TL stereomicroscope lamp positioned approximately 30 cm above
the dish. All adult specimens were then individually placed in the dish, viewed
close-up without magnification, and assigned an index of pigmentation, from 1 to
7, in the following manner: 1 -abdomen lighter than the lightest standard; 2-
abdomen like the lightest standard; 3-abdomen darker than the lightest standard
and lighter than the intermediate standard; 4-abdomen like the intermediate
standard; 5-abdomen darker than the intermediate standard and lighter than the
darkest standard; 6-abdomen like the darkest standard; 7-abdomen darker than
the darkest standard. This procedure was carried out independently by each
author, using the same standards. For most specimens, both authors selected the
same index. When the indices of a specimen differed by one unit, a coin toss
decided the index. When the indices differed by two units (this happened for only
two specimens), the mean was used as the index. Finally, if a specimen’s abdomen
was shrivelled and wrinkled, the index was lowered by one unit, and if an
abdomen was covered by abnormal milky and glossy cuticle, its index was
increased by one.

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ANALYSIS OF VARIATION

The marked geographic variation in habitat and pigmentation observed by the
first author while collecting Jamacian Ischnothele indicated that there might be
more than one species of Ischnothele on the island.

The Blue Mountain populations (Fig. 7) are found at elevations of 3200-5000
feet in what Asprey and Robbins (1953) call upper montane sclerophyll forest and
mist forest. The only other Jamaican Ischnothele specimen from an upland region
is from Burnt Hill, located at an elevation of 1700-2000 feet in the Cockpit region
where the principal natural community is wet limestone forest. Both the Blue
Mountain and Burnt Hill populations experience over 80 inches of rainfall and
only the briefest dry season each year. In contrast, the populations west and east
of Kingston (Fig. 7) are situated on the dry south coast between sea level and 500
feet elevation in cactus thorn scrub and dry limestone forest, respectively. The
former population receives less than 30 inches of rain per year and the latter less
than 45 inches; both experience a long dry season of six to ten months. The mesic
Blue Mountain forest habitat is characterized by a dense ground layer of
vegetation and soils with considerable organic matter, whereas the coastal
habitats have little or no ground vegetation and a rocky, porous, dry substrate,
either solid, jagged, honeycombed limestone rock with almost no humus and
scattered patches of leaf litter (west of Kingston), or loose limestone rock and
gravel with only small amounts of organic matter and scattered patches of leaf
litter (east of Kingston).

Because of the greater density of white setae and the lighter pigmentation under
the abdominal cuticle, all adults from the lowland populations west of Kingston
are much lighter (very light grey) over most of their body and appendages (Figs.
5, 6, 8) than the great majority of adults from the Blue Mountains and Burnt
Hill, which are medium to dark brown (Figs. 3, 4, 8). The lowland sample from
east of Kingston averages darker than the west of Kingston sample and lighter
than the upland sample, and overlaps the pigmentation values of both those
samples (Fig. 8).

The large habitat differences among these populations, especially between the
upland and lowland populations, suggest that very different selection pressures
may be acting on the different populations. The observations that 1) the
coloration of each population approximates the substrate color characteristic of
its habitat and 2) these spiders are often difficult to locate when they have been
forced out of their webs by collectors and are on, or partly buried in, the
substrate, are consistent with this hypothesis. Perhaps selection by visual
predators is responsible for this color variation.

Unsuccessful searches for Ischnothele populations in two areas (see black bars
in Fig. 7) of habitat intermediate in elevation, rainfall, vegetation cover, and
substrate, and lying between the south coast and the backbone of the eastern
mountain mass, suggest that the upland and lowland populations may be
geographically isolated from each other by unsuitable habitat. These areas, along
the Kingston to Newcastle road between Redlight and Mona and along the road
from Port Morant to Bath and west of Bath, both provided geometrically suitable
web sites (rock outcrops and earth road banks), but no Ischnothele webs were
found.

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An additional finding also suggests to us that the Blue Mountain population
and the lowland populations of Ischnothele are geographically isolated and have
diverged genetically; each of these two population clusters harbors a different
species of Mysmenopsis kleptoparasite which are each other’s closest relatives
(Coyle and Meigs 1989).

Our analysis of morphological variation in and among the Ischnothele samples
also supports this hypothesis that the two lowland populations have diverged
markedly from the upland populations, although it should be noted that
especially small male sample sizes limit the rigor of this test. The results of this
analysis are summarized below:

Males : Among the five available males, noteworthy (discontinuous) variation
was observed only in some leg I, pedipalp, and eye characters. The tibia I
apophysis of the three lowland specimens is considerably longer and more sleder
than that of the two upland specimens (Figs. 9, 12-17), but it is noteworthy that
the east of Kingston male’s apophysis (Fig. 16, 17) is not as long as those of the
specimens from west of Kingston (Figs. 14, 15) and widens distally as in the
upland males’ apophyses (Figs. 12, 13) instead of being slightly constricted
distally as in the west of Kingston specimens. Both west of Kingston males have a
more prominent retrolateral metatarsal protuberance (Fig. 14) than do the east of
Kingston (Fig. 16) and upland males (Fig. 12), and they also lack the
ventroretrolateral spine that is present midway between this protuberance and the
distal end of the metatarsus in the east of Kingston and upland males. The
lowland males have more (2-4) prolateral spines on tarsus I (Fig. 19) than do the
upland specimens (0-1) (Fig. 18). The lowland males (Fig. 23) have a deeper
indentation on the ventral face of the palpal organ at the bulb-embolus junction
than do the upland males (Fig. 22). For the east of Kingston male, the silhouette
of the retrolateral surface of the embolus in ventral view is more similar to that
of the other lowland males than to the upland males (Fig. 24), but the reverse is
true of the silhouette of the prolateral surface. The two prolateral spines on the
pedipalp patella are much thicker in the lowland (Fig. 26) than in the upland
males (Fig. 25). In the lowland males, the more proximal of these spines is
especially stout and tapers abruptly to an extremely thin deciduous tip. The
ocular quadrangle of the upland males is proportionally wider than that of the
lowland males (Fig. 10).

Females'. For all meristic and measurement characters, there is considerable
overlap among the samples of the three main population clusters (Blue Mountain
plus Burnt Hill; west of Kingston; and east of Kingston). The least overlap is
found in CTR (Table 2); all but two upland specimens have more retrolateral
cheliceral teeth than all the lowland specimens. Several ratios separate some of
the population clusters (Table 2): OQW(100)/LSL3 (Fig. 11), OQW(100)/CL
(Fig. 10), AMD(100)/ITarS, ITarS(100/CTR, and LSL3(100)/CL. For every one
of these ratios the two lowland samples broadly overlap one another and are
distinct from the upland specimens. The only quantitative character for which
either lowland sample is even roughly intermediate between the other one and the
upland sample is AMD(100)/ITarS, where most of the west of Kingston
specimens are intermediate.

The females from west of Kingston all have distinctively low and relatively
weakly sclerotized median bulbs which are much shorter than the lateral bulbs,

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Figures 12-19. — Jamaican Ischnothele species, male leg I characters; 12, 13, I. reggae holotype,
retrolateral; 12, tibia and metatarsus; 13, tibial apophysis; 14, 15, I. xera holotype, retrolateral; 14,
tibia and metatarsus; 15, tibial apophysis; 16, 17, I. xera E. of Kingston, retrolateral; 16, tibia and
metatarsus; 17, tibial apophysis; 18, 19, holotypes, tarsus, prolateral; 18, I. reggae ; 19, I. xera. Scale
lines: 1.0 mm for Figs. 12, 14, 16, 18, 19; 0.5 mm for Figs. 13, 15, 17.

and the secondary bulb between these two is small and not attached to the lateral
bulb (or may even be missing) (Figs. 33-35). The upland females all have large,
moderately heavily sclerotized median bulbs that are as tall or nearly as tall as
the lateral bulbs, and the secondary bulb is usually, but not always, attached to
the lateral bulb (Figs. 27-29). The spermathecal form of the specimens from east
of Kingston (Figs. 30-32) is intermediate between those of these two samples, but
appears closer to that of the upland sample than to the west of Kingston form.

In conclusion, the data available on variation in habitat, pigmentation,
kleptoparasites, and morphology suggest that the Blue Mountain, east of
Kingston, and west of Kingston populations have diverged genetically and that
the latter two (lowland) have diverged less from each other than from the upland
population. (The observation that the east of Kingston population is intermediate
in several varying characters suggests that the three populations may be remnants
of a once continuously distributed ancestral population that exhibited clinal

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Figures 20-26. — Jamaican Ischnothele species male pedipalp characters; 20, 21, holotype tibia,
cymbium, and palpal organ, retrolateral; 20, I. reggae; 21, /. xera; 22, 23, holotype palpal organ,
ventral aspect of retrolateral; 22, /. reggae ; 23, I. xera ; 24, distal three-fourths of embolus, ventral
view, I. reggae holotype (top), I. xera from E of Kingston (middle), I. xera paratype (bottom); 25, 26,
patella, prolateral; 25, /. reggae holotype; 26, I. xera, E of Kingston. Figures 27-35. — Jamaican
Ischnothele species female spermathecae; 27-31, 33-35, right side only, 32, both sides; 27-29, /. reggae;
27, Blue Mtns. 17 mi. post; 28, Whitfield Hall; 29, Catherine’s Peak; 30-35, /. x era; 30-32, E of
Kingston; 33-35, paratypes. Scale lines: 1.0 mm for Figs. 20, 21, 25, 26; 0.5 mm for Figs. 22-24; 0.1 mm
for Figs. 27-31, 33-35; 0.2 mm for Fig. 32.

variation.) This indicates that it is more likely that intrinsic isolating mechanisms
have evolved between the upland and lowland populations than between the
lowland populations; consequently, we will describe two species of Jamacian
Ischnothele , one from the uplands and one from the lowlands. We want to
emphasize, however, that much more field work is necessary to gather enough
data on geographic distribution, on variation in habitat, morphology, and other
characters, and on reproductive behavior, to be able to rigourously test this and
alternative hypotheses.

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COEVOLUTION

Since the two Jamaican Ischnothele species are each other’s closest relatives,
since each harbors a different species of Mysmenopsis kleptoparasite, and since
these two Mysmenopsis species are also each other’s closest relatives (Coyle and
Meigs 1989), it appears that these hosts and kleptoparasites have cospeciated.
This is the first clear evidence for the kind of host-symbiont cospeciation process
which Platnick and Shadab (1978) suggested might have played a role in
Mysmenopsis evolution. Presumably, the ancestral kleptoparasite species was
fragmented into geographically isolated populations on Jamaica as a result of
fragmentation of the host Ischnothele population, and each set of host/
kleptoparasite populations evolved independently in different environments under
differing selection pressures.

The greater phenotypic difference (particularly in both male and female genital
characters) between the two kleptoparasite sister species than between the two
host sister species indicates that the former may have evolved more rapidly than
the latter. Barnard (1984) lists four parameters which, if they differ between the
host and parasite, may cause asymmetry in the rates of host and parasite
evolution: population size, amount of variation within populations, the tendency
of populations to become fragmented, and generation time. We lack enough
information to evaluate the possible contributions of most of these and other
factors to the apparently faster divergence of the Mysmenopsis populations, but
we suggest that the probable difference in generation times between Mysmenopsis
and Ischnothele could be one important factor. Like other tiny araneomorph
spiders, these Mysmenopsis species probably have a generation time of no more
than one year. Our observations of laboratory growth rates and size frequency
distributions of Ischnothele species (including the Jamaican species) suggest that
the Jamaican Ischnothele require 2 or 3 years to develop from egg to adult. Such
a difference would mean a greater number of recombination and selection bouts
per unit time in the Mysmenopsis populations than in the host Ischnothele
populations; this would favor faster evolution of the kleptoparasite than the host.

Ischnothele reggae , new species
Figs. 1-4, 7-13, 18, 20, 22, 24, 25, 27-29

Types. — Male holotype and 12 female paratypes from roadbanks in humid
montane forest along road between Newcastle (3800 ft. elev.) and Hardwar Gap
(4000 ft. elev.), St. Andrew Parish, Jamaica (8 April 1988 [male molted to
maturity on 24 April 1988]; F. Coyle, R. Bennett, and A. Robinson), deposited in
the American Museum of Natural History.

Etymology. — The specific name is a noun in apposition taken from a popular
genre of Jamaican folk music.

Diagnosis. — The two known males of /. reggae can be distinguished from the
three known males of /. jc era by the following differences: 1) The tibia I
apophysis is shorter (Figs. 9, 12, 13) (TAL = 0.11-0.12) and wider (TAW = 0.23-
0.27) [TAW(100)/TAL = 193-243] than in /. xera (Figs. 9, 14-17) [TAL = 0.26-
0.41; TAW = 0.17-0.19; TAW(100)/TAL = 45-64]. 2) There are fewer prolateral
spines on tarsus I (0-1) (Fig. 18) than in I. xera (2-4) (Fig. 19). 3) The two

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prolateral spines on the pedipalp patella are much more slender and gradually
tapering (Fig. 25) than in I. xera (Fig. 26), in which the more proximal of these
spines is especially stout and tapers abruptly to an extremely thin deciduous tip.
4) The ocular quadrangle is proportionally wider [OQW(100)/CL = 28-29] (Fig.
10) than in /. xera [OQW(100)/CL = 24-25]. 5) The carapace edge setae are
proportionally shorter [CS(100)/CW = 14-15] than in L xera [CS(10Q)/CW = 18-
22]. 6) Dorsal coloration is darker (Figs. 3, 8) than in /. xera (Figs. 5, 8).

Most females of L reggae can be distinguished from those of /. xera by the
following differences: 1) Since the ocular quadrangle is usually proportionally
wider (Fig. 10) and the terminal article of the lateral spinneret is usually
proportionally shorter than in /. xera , OQW(100)/LSL3 is the best ratio
character for separating I. reggae (23-32) from /. xera (18-24) (Fig. 11). 2) CRT is
usually greater (9-12) than in /. xera (7-9). 3) Because of their relatively high CTR
and relatively low ITarS, /. reggae females usually have a lower value for
ITarS(lOO)/ CTR (17-67) and a higher value for AMD( 100) /ITarS (3.5-9.6) than
do I. xera females (56-157, 1.9-3. 8, respectively). 4) Dorsal coloration is usually
darker than in I. xera (Figs. 4, 6, 8).

Males. — Table 1. Palpus (Figs. 20, 22, 24) with large bulb rather clearly
delimited from embolus base; ventral face of bulb-embolus junction only slightly
indented; terminal one-third of embolus slender in lateral view, curved upward
and retrolaterally, with abrupt downward bend just short of tip, with serrations
along retrolateral aspect of dorsal surface. Pedipalp tibia (Fig. 20) subcylindrical
with only slight ventral swelling in proximal half; no enciform spines. Spines on
dorsal aspect of prolateral face of pedipalp patella slender, long, and gradually
tapering (Fig. 25). Tibia I apophysis (Figs. 12, 13) short, broad, with numerous
apical spines ranging from short to very long. Proximal one-third of metatarsus I
(Fig. 12) with strong ventro-retrolateral depression delimited distally by
prominent ventro-retrolateral protuberance associated with more prolateral
ventral keel; distal end of metatarus with ventral keel. Tarsus I flexible because of
weakly sclerotized transverse “seams” over distal two-thirds (Fig. 18). Fovea a
deep strongly procurved groove. One pair of long foveal setae. Bristles around
lateral edges of carapace moderately long. Carapace pale yellow to orange yellow;
chelicerae, pedipalps, and legs slightly darker. Abdominal dorsum with dark
brown background color and 5-6 pairs of light areas; anterior pair largest, oval,
joined by median pale area, other pairs (proceeding from anterior to posterior)
progressively smaller, more obliquely transverse, more nearly united medially
(Fig. 3). White setae not abundant.

Females. — Table 2. Spermathecae with two widely separated primary bulbs on
each side and third, smaller, secondary bulb attached to (usually) or near lateral
bulb (Figs. 27-29). Bulbs usually without stalks, heavily sclerotized; stalk, if
present, short. Median bulb large, as tall or nearly as tall as lateral bulb. Fovea a
deep strongly procurved groove (Fig. 1). One pair of long foveal setae (Figs. 1, 2).
Bristles around edge of carapace moderately long (Fig. 1). Carapace pale yellow
to orange-tan, similar to pedipalps and legs, lighter than chelicerae. Abdominal
dorsum with medium to dark brown background color and 5-6 pairs of light
areas as in males (Figs. 1, 4). White setae not abundant.

Variation.— -See Analysis of Variation section above.

Natural history.— The /. reggae population observed between Newcastle and
Hardwar Gap in the Blue Mountains favors road and trail banks in, or adjacent

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to, moist forest. These banks range from low pebbly soil banks to high rock
banks, some of which are exposed and considerably drier than others. Webs are
abundant, reaching densities as high as five webs per m2 on two different sections
of tall roadbank. Collecting labels indicate that webs are sometimes constructed
in bromeliads. The tubular silk retreats penetrate rock crevices, drill holes, soil
cavities, moss, and leaf litter, and open out via one or two tubular access
passageways onto exposed capture webs composed of one or two roughly
horizontal sheets plus other non-horizontal sheets and strands (sometimes
including vertical strands up to 30 cm long) anchored to surrounding substrates.
A typical /. reggae web has a horizontal capture area of about 400 cm2, but this
value ranges up to 1200 cm2 in the largest webs.

The prey and prey capture behavior of I. reggae are described and discussed
elsewhere by Coyle and Ketner (in press). In the field, these spiders appeared to
be more reluctant to capture prey during the daytime than were other species of
Ischnothele observed by the first author. /. reggae individuals run extremely fast
(Coyle and Ketner in press) and/or feign death when forced out of their webs
onto the ground; this plus their cryptic coloration makes them especially difficult
to collect. Mysmenopsis monticola kleptoparasites were found in many of the
larger /. reggae webs (Coyle and Meigs 1989).

Oviposition was observed in March, April, and May, but may not be limited to
that period (A large number of third postembryonic instar spiderlings were
collected with a female on 4 October 1957). As in the diplurid genus Euagrus
(Coyle 1988), the bright white silk egg sac resembles a shallow silken bowl or
short hammock holding the flattened spherical egg mass and covered with a layer
of silk. It is usually suspended in the wall or floor of the tubular silk retreat. The
/. reggae female tends to rest on the flat top of her egg sac (which is about as
long as her body) or at least close to it, with her legs touching it. Of four egg sacs
collected on 8 April, one contained only eggs, one contained only spiderlings in
the second postembryonic instar (see Galiano 1972 for a description of
postembryonic development in Ischnothele siemensis ), one contained only fully
active and pigmented spiderlings in the third postembryonic instar which
appeared ready to abandon the egg sac, and one had recently been evacuated.
Time from oviposition to evacuation of the egg sac ranged from 2.5 to 4 weeks in
the seven broods produced in captivity. Brood sizes of the eight complete broods
collected ranged from 47 to 100 and averaged 75.0. The three field-collected
broods averaged larger (63-100; 85.6) than the five broods produced in captivity
(47-100; 68.6). Within the first week after evacuating the egg sac, third
postembryonic instar spiderlings did not capture prey (Drosophila) while in their
mother’s capture web even though they could move about quickly and spin silk.
However, when such spiderlings were placed in individual containers, they
constructed webs and captured and ate Drosophila.

Distribution. — Known from elevations above 1700 ft. in the Cockpit Country
of western Jamaica and above 3200 ft. in the Blue Mountains of eastern Jamaica
(Fig. 7).

Material examined.— The type specimens and the following: JAMAICA: PORTLAND PARISH;
17 mi. post, Blue Mountains, tree bases, 28 July 1955 (A. F. Archer and T. H. Farr), 1 female (IJ);
Green Hills, 3750 ft. elev., 10 Sept. 1950 (Sibley), 1 female, juvs. (IJ); Hardwar Gap, 4000 ft. elev., 27
June 1954 (A. Chickering), 4 females, juvs. (MCZ). ST. ANDREW PARISH; Catherine’s Peak, 5000
ft. elev., 26 June 1936, 1 female (USNM); between Catherine’s Peak and Newcastle, road to Clifton
Ht., 4000 ft. elev., 16 July 1950, juvs. (IJ); Cinchona, 4000 ft. elev., Jan. 1912 (C. T. Brues), 2 females

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(IJ); Cinchona Plantation, road to Morce’s Gap, 4000 ft. elev., 22 March 1940 (C. B. Lewis), 1 female
(IJ); Clydesdale, 3500 ft. elev., 7 June 1948 (D. E. Miller), 1 female (AMNH); vicinity of Morce’s Gap
above Clydesdale, 4800 ft. elev., in bromeliads, 19 June 1948 (C. J. Goin), 1 female, juvs. (AMNH);
just W of Silverhill Gap, 3250-3500 ft. elev., in bromeliads, 9 July 1952, 1 female, 1 male, juv.
(AMNH); Yallahs River above Silverhill Factory, in bromeliads, 1 July 1952, juvs. (AMNH). ST.
THOMAS PARISH; Farm Hill Gap, circa 4000 ft. elev., sheet web with funnel retreat in earth bank,
1 May 1950 (G. R. Proctor), 1 female (IJ); Whitfield Hall, 4200 ft. elev., under stones, 13 April 1950
(R. P. Benpry), 3 females, juv. (IJ). TRELAWNY PARISH; Burnt Hill, 1700-2000 ft. elev., under
rocks, 21 July 1985 (G. B. Edwards), 1 female (FSC).

Ischnothele xera , new species
Figs. 5-11, 14-17, 19, 21, 23, 24, 26, 30-35

Types. — Male holotype and one male and four female paratypes from cactus
thorn scrub at Fort Clarence (20-100 ft. elev.) and adjacent part of Hellshire Hills
(20-200 ft. elev.) near Seafort, St. Catherine Parish, Jamaica (9 April 1988
[paratype male molted to maturity in Oct. or Nov. 1988]; F. Coyle, R. Bennett, B.
Freeman, and A. Robinson), deposited in the American Museum of Natural
History.

Etymology. — The specific name refers to the arid nature of this species’ habitat.

Diagnosis. — Refer to the diagnosis for /. reggae .

Males. — Table 1. Palpus (Figs. 21, 23, 24) with large bulb sharply delimited
from embolus base (ventral face of bulb-embolus junction strongly indented);
terminal one-third of embolus slender in lateral view, curved upward and
retrolaterally, with abrupt downward bend just short of slender tapered tip, with
serrations along retrolateral aspect of dorsal surface. 0-1 enciform spines on
prolateral and retrolateral surface of cymbium near tip. Pedipalp tibia (Fig. 21)
subcylindrical with only slight ventral swelling in proximal half; no enciform
spines. Spines on dorsal aspect of prolateral face of pedipalp patella basally thick;
proximal spine especially thick, tapering suddenly to extremely thin deciduous tip
(Fig. 26). Tibia I apophysis (Figs. 14-17) long, relatively slender, with few to
many apical spines ranging from short to very long. Proximal one-third of
metatarsus I (Figs. 14, 16) with strong ventro-retrolateral depression delimited
distally by prominent ventro-retrolateral protuberance associated with more
prolateral ventral keel; distal end of metatarsus with ventral keel. Tarsus I flexible
because of transverse weakly sclerotized “seams” over distal two-thirds (Fig. 19).
Fovea a deep strongly procurved groove. One pair of long foveal setae. Bristles
around lateral edges of carapace very long. Carapace pale yellow to orange-
yellow; recumbent white setae abundant (Fig. 5). Chelicerae, pedipalps, and legs
similar to carapace. Abdominal dorsum with light to medium brown background
color and 5-6 pairs of light areas; anterior 2 pairs largest, oval, joined by median
pale area, other pairs from anterior to posterior progressively smaller, more
obliquely transverse, more nearly united medially; numerous recumbent white
setae (Fig. 5).

Females. — Table 2. Spermathecae (Figs. 30-35) with two widely separated
primary bulbs on each side, usually with third smaller secondary bulb which may
or may not be attached to lateral bulb. Bulbs usually without stalks; stalk, if
present, short. Median bulb varies from low (much shorter than lateral) and
weakly sclerotized to larger (nearly as tall as lateral) and moderately heavily
sclerotized. Fovea a deep strongly procurved groove. One pair of long foveal

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setae. Bristles around edge of carapace very long. Carapace pale-yellow to
orange-tan; recumbent white setae usually abundant peripherally and sometimes
elsewhere on carapace (Fig. 6). Pedipalps and legs similar to carapace, chelicerae
darker. Abdominal dorsum (Fig. 6) with light grey-brown to medium brown
background color and pattern of 5-6 pairs of light areas as in males; recumbent
white setae numerous to abundant.

Variation. — See Analysis of Variation section above.

Natural history. — The populations studied west of Kingston live in hot, dry,
cactus thorn scrub on honeycombed limestone substrate with very little soil. Webs
are usually found where retreat tubes can penetrate the otherwise sparse leaf litter
that accumulates at the bases of rocks and in some of the holes and crevices in
the soild rock substrate. The population studied east of Kingston lives in dry
limestone forest on a rocky hillside and is much denser than the population west
of Kingston. The webs are most often at the bases of rocks, trees, and exposed
roots and their retreats penetrate the loose limestone pebble substrate. Ischnothele
xera webs are similar in shape to those of /. reggae , but tend to be smaller.

Prey capture behavior is described by Coyle and Ketner (in press). Ischnothele
xera , like /. reggae , is reluctant to capture prey in daylight, is extremely fast, and
sometimes feigns death when forced out of the web onto the ground.
Mysmenopsis furtiva kleptoparasites were found living in the webs of adult I.
xera (Coyle and Meigs 1989).

The adult male collected on 9 April west of Kingston was in the retreat of what
appeared to be his own functional capture web. Four /. xera broods were
collected on 9-10 April: one egg sac contained only spiderlings still in embryonic
cuticle with split and wrinkled chorions still attached, one sac contained active
third postembryonic instar spiderlings which were about to emerge from the sac,
and two recently emerged and fully active third instar broods were found in their
mothers’ retreats. These stages conform to the pattern of early postembryonic
development described by Galiano (1972) for Ischnothele siemensis. One /. xera
female oviposited in captivity on 10 May. The two complete /. xera broods
collected (both from the population east of Kingston) are larger (125 and 137)
than all eight known /. reggae broods (47-100).

Distribution. — Known only from two areas of low elevation along the south
coast of eastern Jamaica (Fig. 7).

Material examined. — The type specimens and the following: JAMAICA: ST. CATHERINE
PARISH: Port Henderson Hill, 250-500 ft. elev., 21 August 1952 (G. Underwood), 1 female (MCZ).
ST. THOMAS PARISH; route A4, 14-15 mi. E Kingston, about 300 ft. elev., dry limestone forest, 10
April 1988 (F. Coyle, R. Bennett, B. Freeman, and A. Robinson), 1 female, juvs. (AMNH); 14 mi. E
Kingston, Morant Bay Road, below 250 ft. elev., 4 October 1957 (A. Chickering), 1 female, 1 male,
juvs. (MCZ); 12 mi. E Kingston, about 200 ft. elev., 11 November 1957 (A. Chickering), 1 female
(MCZ).

Note added in proof:

Three males, two from the I. reggae type locality and one from the I. xera type
locality, have recently matured in our laboratory. With the following three
exceptions, their character states lie within the ranges of the diagnostically useful
characters of the previously studied conspecific samples: 1) The tibia 1 apophyses
of the new /. reggae specimens are longer (TAL = 0.14 and 0.18 mm) and
narrower (TAW = 0.22 and 0.20 mm), and thus the TAW(1G0)/TAL values are
considerably lower (160 and 116) than in the two conspecifics. 2) OQW(100)/CL

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111

for the I. xera specimen is 26, which is slightly higher than that of its three
conspecifics. 3) Two of the new males have similar CS(100)/CW values (/. reggae
= 16.7, /. xera = 17.3) which lie between the ranges of the two previously
described species samples. These new data reduce the usefulness of two of the
seven diagnostic characters that separate the males of /. reggae and L xera ,
however they are consistent with the hypothesis that these are different species.

ACKNOWLEDGMENTS

We are grateful to Mr. Robert Bennett, Dr. Brian Freeman, and Mr. Abraham
Robinson for their help in collecting Ischnothele in Jamaica. The following
persons and institutions kindly loaned Ischnothele specimens for study: Dr. N. I.
Platnick, American Museum of Natural History (AMNH); Dr. G. B. Edwards,
Florida State Collection (FSC); Dr. T. H. Farr, Institute of Jamaica (IJ); Dr. H.
W. Levi, Museum of Comparative Zoology (MCZ); Dr. J. A. Coddington,
National Museum of Natural History, Smithsonian Institution (USNM). Drs. C.
E. Griswold and N. I. Platnick provided helpful reviews of our manuscript. This
study was supported by National Science Foundation Grant BSR-8700298.

LITERATURE CITED

Asprey, G. E and R. G. Robbins. 1953. The vegetation of Jamaica. Ecol. Monographs, 23(4):359-409.
Barnard, C. J. 1984. The evolution of food-scrounging strategies within and between species. Pp. 95-
126, In Producers and Scroungers. (C. J. Barnard, ed.). Chapman and Hall, New York.

Coyle, F. A. 1988. A revision of the American funnelweb mygalomorph spider genus Euagrus
(Araneae, Dipluridae). Bull. Amer. Mus. Nat. Hist., 187:203-292.

Coyle, F. A. and N. Ketner. In press. Observations on the prey and prey capture behaviour of the
funnelweb mygalomorph spider genus Ischnothele (Araneae, Dipluridae). Bull. Brit. Arachnol. Soc.
Coyle, F. A. and T. E. Meigs. 1989. Two new species of kleptoparasitic Mysmenidae (Araneae,
Mysmenoidae) from Jamaica. J. Arachnol., 17:59-70.

Galiano, M. E. 1972. El desarrollo postembryionario larval de Ischnothele siemensi Cambridge, 1896
(Araneae, Dipluridae). Physis, (82): 169-177.

Platnick, N. I. and M. U. Shadab. 1978. A review of the spider genus Mysmenopsis (Araneae,
Mysmenidae). Am. Mus. Novitates, (2661): 1-22.

Manuscript received August 1989, revised October 1989.

1990. The Journal of Arachnology 18:1 13

RESEARCH NOTES

AN EXAMPLE OF PARTIAL DUPLICATION OF
THE ABDOMEN IN NEOBISIUM SIMONI
(PSEUDOSCORPIONES, NEOBISIIDAE)

Records of abdominal anomalies in the pseudoscorpion family Neobisiidae are
very sparse in the older literature (Kastner 1927; Redder 1965). Only recently,
comparative aspects of teratological variation have been studied in six European
species belonging to the genera Neobisium Chamberlin and Roncus L. Koch
(Curcic 1980, 1989; Curcic and Dimitrijevic 1982, 1984, 1985, 1986; Curcic et al.
1981, 1983). These studies have revealed the outstanding heterogeneity of
segmental anomalies affecting abdominal sclerites in the species analyzed. The
sclerite deficiencies in different species of the family Neobisiidae have been found
mostly in the adult stage or occasionally in the tritonymph (Curcic 1989). No
deficiencies have been observed in the preceding instars (deutonymph and
protonymph).

In a collection of pseudoscorpions made by one of us (RND) at Passarole, near
Moulis (Ariege), France, during July 1987, one anomalous protonymph of
Neobisium simoni (L. Koch) was collected. This specimen was obtained from the
leaf litter and humus in a mixed oak forest. In the protonymph studied, only the
dorsal sclerites were aberrant, the ventral sclerites and the appendages were
normal in all respects.

The aim of this note is to describe the phenomenon of tergal teratology of the
aberrant protonymph. All tergites of this specimen are anomalous (Fig. 1). Thus,
tergite I lacks a section on the right; in addition, the number of setae on this
sclerite is reduced. Abdominal tergites II-VI are duplicated on either side of the
mid-line (thus forming separate “demi-tergites”), and their form and distribution
are drastically changed in relation to those in normal protonymphs of N. simoni.
Tergite VII is fused with the left part of tergite VIII and as well as with the right
section of tergite IX. An isolated section of tergite VIII is present on the right.
Furthermore, tergites VIII-IX and IX-X have developed a bicyclical sinistral
helicomery. An isolated part of tergite X is present on the left. As a consequence
of the deficiencies noted, the tergal setation in this specimen is significantly
altered in relation to normal setal complement (which is, for tergites I-X, 44-44-
44-4-4-4-4). Altogether, five types of teratologies have been found to affect the
abdominal tergites in this protonymph: hemimery, atrophy, symphysomery,
helicomery and tergite enlargement.

The majority of the abdominal deficiencies in neobisiid species occur during the
transformative development of tritonymph into adult (Cur£ic and Dimitrijevic
1986). It appears likely that the origin of such anomalies may be induced by some
irregularity in the process of molting. Considerably fewer specimens become

1990. The Journal of Arachnology 18:114

anomalous when transforming from deutonymph into protonymph (Curcic et al.
1983), or even from the protonymph into deutonymph stage, as was shown by
Pedder (1965) for representatives of families other than Neobisiidae.

Since the aberrant example of N. simoni is a protonymph, the genesis of its
deficiencies remains obscure. However, one may assume that the origin of the
drastically modified abdominal tergites in this specimen could be found among
the genetical (or some morphogenetic) factors, which influence the pre-molting
period of the ontogenetic process.

We are grateful to C. Juberthie, Director of the Laboratoire southerrain in
Moulis, for his collaboration, help and permission to use the laboratory facilities
and to collect pseudoscorpions in the vicinity of Moulis. We are also grateful to
W. B. Muchmore and V. F. Lee for their valuable comments and constructive
criticism of the manuscript.

1990. The Journal of Arachnology 18:115

LITERATURE CITED

Cur£i6, B. P. M. 1980. Accidental and teratological changes in the family Neobisiidae
(Pseudoscorpiones, Arachnida). Bull. Brit. Arachnol. Soc., 5:9-15.

CurCic, B. P. M. 1989. Segmental anomalies in some European Neobisiidae (Pseudoscorpiones,
Arachnida) - Part L Acta Arachnol, 37:77-87.

CurCic, B. P. M. and R. N. Dimitrijevic. 1982. On abnormalities of abdominal segmentation in
Neohisium carpaticum Beier (Neobisiidae, Pseudoscorpiones, Arachnida). Rev. Arachnol, 4:143-
150.

Curdic, B. P. M. and R. N. Dimitrijevic. 1984. An abnormal carapaco-abdominal junction in
Neobisium carpaticum Beier, 1934 (Neobisiidae, Pseudoscorpiones). Arch. Sci. Biol Belgrade,
36:9P-10P.

CurCic, B. P. M. and R. N. Dimitrijevic. 1985. Abdominal deficiencies in four species of the
Neobisiidae (Pseudoscorpiones, Arachnida). Rev. Arachnol, 6:91-98.

Curcic, B. P. M. and R. N. Dimitrijevic. 1986. Abnormalities of carapacal and abdominal
segmentation in Neobisium Chamberlin (Neobisiidae, Pseudoscorpiones). Actas X Congr. Int.
Aracnol. Jaca/Espana 1986, 1:17-23.

Curihc, B. P. M., M. D. Krunic and M. M. Brajkovic. 1981. Further records of teratological changes
in the Neobisiidae (Arachnida, Pseudoscorpiones). Bull. Brit. Arachnol. Soc., 5:280-284.

Curcic, B. P. M., M. D. Krunic and M. M. Brajkovic. 1983. Tergal and sternal anomalies in
Neobisium Chamberlin (Neobisiidae, Pseudoscorpiones, Arachnida). J. Arachnol, 11:243-250.
Kastner, A. 1927. Pseudoscorpiones. Pp 1-66, In Biologic der Tiere Deutschlands, (P. Schulze, ed.).
Berlin.

Pedder, I. J. 1965. Abnormal segmentation of the abdomen in six species of British pseudoscorpions.
Entomologist (London), 98:108-112.

B. P. M. Curcic and R. N. Dimitrijevic, Institute of Zoology, Faculty of
Science, University of Belgrade, 16, Studentski Trg, YU-11000 Beograd,
Yugoslavia.

Manuscript received May 1989, revised July 1989.

A NEW SPECIMEN OF MICROTIT YUS AMBARENS1S
(SCORPIONES, BUTHXBAE), FOSSIL FROM HISPANIOLA:
EVIDENCE OF TAXONOMIC STATUS
AND POSSIBLE BIOGEOGRAPHIC IMPLICATIONS

Three fossil buthid scorpions have been described from Hispaniola, all from
single juveniles embedded in Dominican amber: Cenlruroides beynai Schawaller,
1979, Tituyus geratus Santiago-Blay and Poinar, 1988, and T. ambarensis
Schawaller, 1982. Whereas in the type species of the genus, Microtityus rickyi
Kjellesvig-Waering, 1966, femoral trichobothrium d 2 is absent, M. ambarensis
bears it, providing one of the main reasons for its original placement in Tityus.
Scrutiny by several researchers led to the suspicion that I ambarensis may
belong to Microtityus Kjellesvig-Waering, 1966. Armas (1988) transferred T.
ambarensis to Microtityus without having available the holotype or other
specimens (Armas to Schawaller 29 May 1987; Schawaller to Armas 8 July 1987;
in litt.). Evidence from a new fossil specimen now supports the placement of T

1990. The Journal of Arachnology 18:116

Figures l, 2. — Microtityus ambarensis (new
specimen): 1, dorsal view, note three dorsal
mesosomal keels (arrowhead points one keel);
2, ventral view, note suboval spiracles
(arrowhead points one spiracle).

ambarensis in Microtityus. We also discuss possible biogeographic interpretations
of this find in light of a vicariance model
The new scorpion, which is 7.6 mm long, is in a piece of amber believed to
have come from La Toca mine, Northern Dominican Republic. Amber from that
mine has been dated as approximately 30=40 million years old (Lambert et al.
1985). The exact origin of the amber piece with the holotype of T. ambarensis is
not clear. Based on the ratio of the overall total lengths (1.2), we conclude that
the new specimen is a second instar, one instar less than the holotype. Two of the
three dorsal mesosomal keels are evident (Fig. 1) and the spiracles are relatively
small and suboval (Fig. 2); these are critical qualitative generic characters
obscured in the holotype (Armas 1988). The dentition of the pedipalp movable
finger is almost non-overlapping and there is a small pectinal tooth count (10-11,
for this species), as typical of Microtityus. The full complement of pedipalp
femoral trichobothria present in this specimen distinguishes the taxon from the
small South American buthid Mesotityus Gonzalez-Sponga, 1982. The holotype

1990. The Journal of Arachnology 18:117

was, in contrast to its description, originally illustrated with eight, instead of
seven, mesosomal tergites (Schawalier 1982).

With the exception of M. ambarensis , all other described species of Microtityus
are extant; all are small (< 25 mm long at adulthood). Microtityus ambarensis
can be distinguished from M. dominicanensis Santiago-Blay, 1985 and M.
consuelo Armas and Marcano Fondeur, 1987 by the number of pedipalp finger
rows and pectine tooth number: M. dominicanensis has 10 rows and 8 teeth; M.
consuelo has 11 rows and 14 teeth.

The genus Microtityus is neotropical buthid taxon known from Brazil,
Venezuela, Trinidad, Virgin Islands, Dominican Republic, Haiti (Santiago-Blay,
in prep.), and Cuba. The genus has not been reported for Jamaica, Puerto Rico
or the Lesser Antilles. We suggest that when the Caribbean plate(s) first contacted
the South American plate about 60-80 mya (Pindell and Barrett, in press),
ancestors of today’s Caribbean Microtityus fauna migrated from the south.
However, although the Caribbean plate seems to have been in contact with
continental land masses, direct dry land connections have not been proven. We
cannot indicate whether the arrival of Microtityus to the area was a product of
vicariant or dispersal events. Further splitting and accretion of the Greater
Antilles land masses produced subsequent vicariant events reponsible for the
development of a 100% endemic Microtityus fauna.

J. Yellen kindly allowed author JASB to study the specimen and provided the
data on the probable collection site of the new fossil piece. P. Craig and J. Yellen
did the photographic work. E. E. Williams, M. Perfit, J. L. Pindell, G. A. Polis,
W. D. Sissom and S. Stockwell reviewed the manuscript and suggested changes.
The authors are most grateful to them all.

LITERATURE CITED

Armas, L, F. de. 1988. Situacion taxonomica de Tityus ambarensis (Scorpiones; Buthidae) escorpion

fosil de Republica Dominicana. Garciana, 11:1-2.

Lambert, J. B., J. S. Frye and G. O. Poinar, Jr. 1985. Amber from the Dominican Republic: Analysis
by nuclear magnetic resonance spectroscopy. Archaeometry, 27:43-51.

Pindell, J. L. and S. F. Barrett. 1988. Geological evolution of the Caribbean Region; A plate-tectonic
perspective. In The Caribbean Region. The Geology of North America. (G. Dengo and J. E. Case,
eds.). Vol. H. Geological Society of America. Boulder, CO. (In press).

Schawalier, W. 1982. Zwei weitere Skorpione in Dominikanischem Berstein (Stuttgarter
Bernsteinsammlung: Arachnida; Scorpionida). Stutt. Bietr. Natur. (Geol. Palaontol.), Ser. B, 82:1-14.

Jorge A. Santiago-Blay, Department of Entomological Sciences, University of
California, Berkeley, California 94720, USA; Wolfgang Schawalier, Staatliches
Museum fur Naturkunde, Stuttgart 1, Federal Republic of Germany and George
O. Poinar, Jr. Department of Entomological Sciences, University of California,
Berkeley, California 94720.

Manuscript received March 1989 , revised July 1989.

1990. The Journal of Arachnology 18:118

A ZYGOMYCETOUS FUNGUS AS A MORTALITY FACTOR
IN A LABORATORY STOCK OF SPIDERS

The first instars of our laboratory stocks of several spider species are usually
fed with fruit flies, Drosophila melanogaster. In 1987 and 1988, we noticed a
disease in several hatchling groups of Cupiennius salei Keyserling (Ctenidae) and
Ischnothele guyanensis Walckenaer (Dipluridae). The spiders did not accept food
and did not move very much. They sat most of the time on the bottom of the
box (instead of hanging under the lid) and their appearance became dark and
wet. Such spiders died 2-6 weeks after these symptoms were recognized.

The infection rate of a given hatchling group (50-100 spiderlings) was about 90-
100% and probably all infected spiders died (total N of dead spiders >500). We
do not know whether the surviving spiders had not been infected or whether they
successfully fought the infections. When the disease was recognized at an early
stage, some techniques could increase the survival rate to approximately 20-30%.
We tried several breeding techniques and found the following methods to lower
spider mortality: Low air humidity (<70%), no free water, cleaning the box once
a week, lids with additional slits to provide a better air circulation and no
Drosophila food. The relative success of our changed breeding technique
indicated that our spiders had probably been infected by a pathogen which
originated from our Drosophila culture. Since Drosophila vials house a wide
range of fungi in the food medium of the larvae, it is possible that the flies
function as a vector for these pathogeneic fungi when fed to the spiders.

To test this assumption we anaesthetized a total of 22 Ischnothele and 8
Cupiennius from different breeding groups by CO2, cut off the opisthosoma
under sterile conditions, disinfected the cuticle with ethanol (70%), opened the
body ventrally with fine scissors and took a tissue sample with a sterile needle.
The tissue was inoculated on Petri dishes and cultured on malt agar at 20° C.
After 1-2 days the first fungal colonies could be detected. For further
identification some fungus colonies were selectively transferred to new Petri
dishes and cultured and propagated as above.

From all spider samples we were able to isolate the zygomycete Mucor hiemalis
/. hiemalis (Figs. 1-5). This identification was confirmed by W. Gams and M. A.
A. Schipper. This fungus is distributed worldwide and common in the soil or on
plants (Zycha et al. 1969). It is known to kill honey bees (Burnside 1935) and
several Lepidoptera, Coleoptera and Diptera species (Heitor 1962), but causes
also a tomato disease (Zycha et al. 1969).

From some spider samples we could further isolate on unidentified fungus
imperfectus. In nearly all spiders high numbers of bacteria were found. A
microscopic examination of the tissue sample soon after the dissection of the
spider revealed that the intestinal tract of most spiders contained up to three
different bacterial forms. We did not make further efforts to identify them.

How does the fungus infect the spider? Since the spiders feed on infected
Drosophila flies, we first thought that the fungus enters the spider’s body via
spores which survive the extraoral ingestion and pass through the prosoma filter
system. An inhibition test with a suspension of M. hiemalis spores (106 spores/
ml) on agar plates and 2p\ digestive fluid of Cupiennius did not prevent the

1990. The Journal of Arachnology 18:1 19

Figures 1-5. — The zygomycete Mucor hiemalis f hiemalis Wehmer, isolated from a laboratory stock
of spiders (interferential contrast microscope): 1, the primitive siphonal mycelium, grown from
sporangiospores in a submers culture; 2, two sporangia with a dissolved sporangial wall; 3, empty
sporangium, columella with remnants of the sporangium wall; 4, sporangiospores of different sizes; 5,
spherical gemmae at older mycelium (slide culture).

spores from germinating. This indicates that M. hiemalis spores could survive the
ingestion by a spider, although the digestion of fungus spores could be shown for
orb-weaving spiders (Smith and Mommsen 1984). But could the spores pass
through the prosoma filter? Though particles >1 jam are normally retained by the
effective filter system, larger particles such as pollen or spores can pass it as well
(Collatz 1987). To test this assumption, we injected 20 jtd of a spore suspension
(106 spores/ ml) into crickets which were fed to spiders. We chose spores of
varying size (from 1 to 10 jam) from three fungus species: two tropical fungi (to
exclude possible error and interpretation problems) and M. hiemalis. The spiders
(N = 15) were killed and tissue samples from the opisthosoma and prosoma
(behind the filter) were inoculated on malt agar. In no case could fungal growth
be observed. This indicates that the infection by M. hiemalis spores probably
does not occur during the normal feeding procedure.

1990. The Journal of Arachnology 18:120'

Greenstone et al. (1987) succeeded in infecting spiders with the pathogenic
hyphomycete Nomuraea atypicola by topical application of a spore suspension
and Heitor (1962) mentions that M. hiemalis can infect insects through injuries.
So it is possible that the infection by this fungus occurs through microscopic
lesions of the cuticle or other sensitive openings (book lungs?).

Is the infection of spiders by M. hiemalis a mere laboratory effect caused by
contact with infected food items or does it occur regularly among free-living
spiders as well? To answer this question we collected 10 spiders representing 10
different species from other parts of the building where our laboratory spiders
were bred ( Pholcus phalangioides (Fuesslin) (Pholcidae), Dysdera crocota C. L.
K. (Dysderidae) and Tegenaria sp. (Agelenidae)) and from nearby parts of the
campus ( Argiope bruennichi (Scopoli), Larinioides cornutus (Clerck) Araneus
diadematus Clerck (Araneidae), Pisaura mirabilis (Clerck) (Pisauridae), Linyphia
triangularis (Clerck) (Linyphiidae), Clubiona sp. (Clubionidae) and Xysticus sp.
(Thomisidae)). The spiders were treated as mentioned above and malt agar Petri
dishes were inoculated. In no case could any fungal growth be found. This
probably indicates that the infection by M. hiemalis is restricted to our laboratory
stock, although the wide dispersion of the fungus could enable it to be a more
common pathogen of spiders.

At the end of 1988, the complete laboratory stock of Cupiennius salei was
moved from Regensburg to Bern. The spiders were housed in rooms where no
Drosophila have been bred before. All plastic containers were replaced by new
materials and the spiders were exclusively fed with crickets. Under these
conditions no fungal disease of the previous epidemic dimension could be
observed and the survival rate of hatchlings was about 90-100% during the first 3-
4 instars ( N > 800). This can be understood as a further argument for a
correlation between Drosophila food, fungal infection and spider mortality
(though it does not prove a cause and effect relationship).

Until now true pathogenic fungi of spiders were only known from Ascomycetes
(the genera Cordyceps and Torrubiella , Clavicipitales) and from their
hyphomycete anamorphs (Gibe Hula, Nomuraea and 7 other genera), the imperfect
fungi (Nentwig 1985; Evans & Samson 1987). No fungi pathogenic to spiders are
known from the Myxomycetes or from the Basidiomycetes. The herein reported
case of M. hiemalis is probably the first observed pathogenic example from the
Zygomycetes. Although we present here only a laboratory case, it is possible that
Zygomycetes infect spiders under natural conditions as well. An interesting
feature of the zygomycete pathogens is the apparent lack of host specifity.
According to our knowledge, pathogenic fungi of spiders do not infect insects and
the insect pathogenic fungi (e.g., Entomophthorales) do not infect spiders (Evans
and Samson 1987). In contrast to this, M. hiemalis seems to have a wide host
range and includes insects and spiders.

We thank W. Gams and M. A. A. Schipper for the confirmation of the fungus
identification and critique of an earlier draft, B. Kellerer and Th. Forst for
technical assistance.

LITERATURE CITED

Burnside, C. E. 1935. A disease of young bees caused by a Mucor. Amer. Bee J., 25:75-76.

1990. The Journal of Arachnology 18:121

Collatz, K. G. 1987. Structure and function of the digestive tract. Pp. 229-228, In Ecophysiology of
Spiders. (W. Nentwig, ed.). Springer, Heidelberg.

Evans, H. C. and R. A. Samson. 1987. Fungal pathogens of spiders. Mycologist, 152-159.

Greenstone, M. H., C. M. Ignoffo and R.A. Samson. 1987. Susceptibility of spider species to the
fungus Nomourea atypicola. J. Arachnol., 15:266-268.

Heitor, F. 1962. Wound parasitism by the fungus Mucor hiemalis Wehner in insects. Ann. Epiphyt.,
13:179-203.

Nentwig, W. 1985. Parasitic fungi as a mortality factor of spiders. J. Arachnol., 13:272-274.

Smith, R. B. and T. P. Mommsen. 1984. Pollen feeding in an orb-weaving spider. Science, 226:1330-
1332.

Zycha, H., R. Siepmann and G. Linnemann. 1969. Mucorales. Cramer, Vaduz.

Wolfgang Nentwig, Zoologisches Institut der Universitat, Baltzerstr. 3, CH-
3012 Bern, Switzerland, and Hansjorg Prillinger, Institut fur Botanik der
Universitat, Universitatsstr. 31, D-8400 Regensburg, F. R. Germany.

Manuscript received May 1989, revised August 1989.

■ i

■

THE AMERICAN ARACHNOLOGICAL SOCIETY

President:

George W. Uetz (1989-1991)
Department of Biological Sciences
University of Cincinnati
Cincinnati, Ohio 45221

Secretary :

James W. Berry (1989-1991)
Department of Biological Sciences
Butler University
Indianapolis, Indiana 46208

President-Elect:

Allen R. Brady (1989-1991)
Biology Department
Hope College
Holland, Michigan 49423

Treasurer:

Gail E. Stratton (1989-1991)
Department of Biology
Albion College
Albion, Michigan 49224

Archivist:

Vincent D. Roth

Box 136

Portal, Arizona 85632

Membership Secretary:

Norman I. Platnick (appointed)
American Museum of Natural History
Central Park West at 79th Street
New York, New York 10024

Directors:

J. A. Coddington (1988-1990), Petra Sierwald (1989-1991), William A. Shear
(1989-1991).

Honorary Members:

P. Bonnet, W. J. Gertsch, H. Homann, H. W. Levi, G. H. Locket, A. F. Millidge,
M. Vachon, T. Yaginuma.

The American Arachnological Society was founded in August, 1972, to
promote the study of Arachnida, to achieve closer cooperation between amateur
and professional arachnologists, and to publish The Journal of Arachnology.

Membership in the Society is open to all persons interested in the Arachnida.
Annual dues are $30.00 for regular members, $20.00 for student members and
$70.00 for institutions. Correspondence concerning membership in the Society
must be addressed to the Membership Secretary. Members of the Society receive
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American Arachnology, edited by the Secretary, contains arachnological news
and comments, requests for specimens and hard-to-find literature, information
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CONTENTS

THE JOURNAL OF ARACHNOLOGY

VOLUME 18 Feature Articles NUMBER 1

Spiders in United States field crops and their potential effect on

crop pests, O. P. Young and G. B. Edwards 1

Observations on the natural history of a New England population of
Sphodros niger (Araneae, Atypidae), Robert L. Edwards and

Eric H. Edwards 29

Water and hemolymph content in the wolf spider Lycosa ceratiola

(Araneae, Lycosidae), James E. Carrel 35

Karyotypes of seventeen USA spider species (Araneae, Araneidae,

Gnaphosidae, Loxoscelidae, Lycosidae, Oxyopidae, Philodromidae,

Salticidae and Theridiidae), Cathy R. Tugman , Judy E. Brown ,

and Norman V Horner 41

El comportamiento agonistico de hembras adultas de Lycosa tarentula
fasciiventris (Araneae, Lycosidae), Carmen Fernandez-Montraveta y

Joaquin Ortega 49

Is it the size that counts? Palp morphology, sperm storage, and egg
hatching frequently in Nephila clavipes (Araneae, Araneidae),

Jeffrey Cohn 59

The size of spider eggs and estimates of their energy content,

John F. Anderson 73

A new species of Linothele from Colombia (Araneae, Mygalomorphae,

Dipluridae), Nicolas Paz S. and Robert J. Raven 79

The effect of time and temperature on disturbance behaviors shown
by the orb-weaving spider Uloborus glomosus (Uloboridae),

Paula E. Cushing and Brent D. Opell 87

Two new species of Ishnothele funnelweb spiders (Araneae, Mygalomorphae,
Dipluridae) from Jamaica, Fredrick A. Coyle 95

Research Notes

An example of partial duplication of the abdomen in Neobisium simoni

(Pseudoscorpiones, Neobisiidae), B. P. M. Curcic and R. N. Dimitrijevic 113

A new specimen of Microtityus ambarensis (Scorpiones, Buthidae), fossil
from Hispaniola: Evidence of taxonomic status and possible biogeographic
implications, Jorge A. Santiago-Blay , Wolfgang Schawaller and

George O. Poinar , Jr 115

A zygomycetous fungus as a mortality factor in a laboratory stock of
spiders, Wolfgang Nentwig and Hansjorg Prillinger 118

Cover photograph, web of Philoponella vicina
(O. Pickard-Cambridge) (Uloboridae) by Jonathan A. Coddington
Printed by PrinTech, Lubbock, Texas, USA
Posted at Lubbock', Texas, 29 June 1990

r3 The Journal of

ARACHNOLOGY

OFFICIAL ORGAN OF THE AMERICAN ARACHNOLOGICAL SOCIETY

VOLUME 18

SUMMER 1990

NUMBER 2

THE JOURNAL OF ARACHNOLOGY

EDITOR: James E. Carico, Lynchburg College
ASSOCIATE EDITOR: Gary L. Miller, The University of Mississippi
EDITORIAL BOARD: J. E. Carrel, University of Missouri; J. A. Coddington,
National Museum of Natural History, Smithsonian Institution; J. C.
Cokendolpher, Lubbock, Texas; F. A. Coyle, Western Carolina University; C.
D. Dondale, Agriculture Canada; W. G. Eberhard, Universidad de Costa Rica;
M. E. Galiano, Museo Argentino de Ciencias Naturales; M. H. Greenstone,
BCIRL, Columbia, Missouri; N. Y. Horner, Midwestern State University; D.

T. Jennings, NEFES, Morgantown, West Virginia; V. F. Lee, California
Academy of Sciences; H. W. Levi, Harvard University; E. A. Maury, Museo
Argentino de Ciencias Naturales; N. I. Platnick, American Museum of
Natural History; G. A. Polis, Vanderbilt University; S. E. Riechert, University
of Tennessee; A. L. Rypstra, Miami University, Ohio; M. H. Robinson, U.S.
National Zoological Park; W. A. Shear, Hampden-Sydney College; G. W.

Uetz, University of Cincinnati; C. E. Valerio, Universidad de Costa Rica.

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Kotzman, M. 1990. Annual activity patterns of the Australian tarantula Selenocosmia stirlingi
(Araneae, Theraphosidae) in an arid area. J. Arachnoh, 18:123-130.

ANNUAL ACTIVITY PATTERNS OF THE AUSTRALIAN
TARANTULA SELENOCOSMIA STIRLINGI
(ARANEAE, THERAPHOSIDAE) IN AN ARID AREA

Mandy Kotzman

Zoology Department, Monash University
Clayton, Victoria, Australia, 3 1 68 1

ABSTRACT

Activity patterns of a population of the burrow-dwelling theraphosid spider, Selenocosmia stirlingi
Hogg, at Coombah (N.S.W.) are reported. Burrows were located and monitored at about 6-weekly
intervals over a period of 3 years while rainfall and diurnal temperature profiles of the soil were also
recorded. Spider activity was determined both from the condition of the burrow entrance and from
the presence of the spider at the burrow entrance during the night. Activity was greatest in spring and
late summer/ fall, with low levels of activity in both winter and mid-summer. It is likely that the
temperature profile in the soil was exploited behaviorally by the spiders in order to thermoregulate.
Estimated losses of spiders from the population were greatest in spring and early summer, and may be
due predominantly to maturing males leaving their burrows in search of females.

INTRODUCTION

Stradling (1978) determined that the tarantula Avicularia avicularia Linnaeus
matured in 3-4 years in the tropical conditions of Trinidad, compared to a
projected development period of 10 years for an arid zone species, Dugsiella
henlzi (Girand), in Arizona (Baerg 1958). Stradling’s (1978) data showed that the
variation in size increase and instar duration increased as the spiders grew. It
therefore seemed likely that environmental factors, such as food availability (e.g.,
Turnbull 1962, 1965), temperature (e.g., Peck & Whitcomb 1970) and

photoperiod (Peck & Whitcomb 1970) might cause these accumulated differences.

In Australia, Selenocosmia stirlingi Hogg occurs throughout arid areas in the
center of the continent, and its range extends into northern tropical regions
(Main 1964). The environmental variation across its range suggested that it would
be an appropriate candidate for the investigation of phenotypic plasticity in
growth and development. Investigations of the field ecology of S. stirlingi formed
part of a broader study of the influence of environmental factors on the spider’s
growth and development (Kotzman 1986). The field study described here was
undertaken to characterize the arid environment in which these spiders live
(particularly in terms of temperature) and to establish the spiders’ natural activity
patterns in the context of these conditions. As these spiders occupy deep burrows
and forage nocturnally from the burrow entrance, “activity” was measured by

‘Current Address: Division of Environmental Studies, University of California, Davis, CA 95616,
U.S.A.

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indications of the spider’s use of the burrow entrance. Diurnal variations in soil
temperatures were recorded, rainfall records were obtained from the nearby
homestead, and the condition of marked burrows and activities of their occupants
were monitored. From these observations, a general picture of the relationships
between the activities of the spiders and the changing environmental conditions
was derived.

STUDY AREA AND METHODS

Distribution of S. stirlingi is patchy, and only after thorough searching was a
study site chosen (about 180 X 450 m) about 5 km south of the Coombah
homestead, on the east side of the Silver City Highway 136 km north of
Wentworth (New South Wales). The site consisted of a central swale bordered on
the north and south by sandhills, and to the east by a claypan, with a total relief
of about 7 m (Fig. 1). Ground cover varied enormously during the study, from
virtually none to dense grasses and herbs. In general, vegetation of the area is
described as a Belah-rosewood community, including scattered trees ( Casuarina
sp.) about 100 m apart, with “blue bush”, herbs and grasses beneath
(Cunningham et al. 1981). During each visit, at approximately 6-week intervals,
new burrows were located by systematically searching the length and breadth of
the field site. Each new burrow was marked with a wooden stake (placed 150 mm
west of the burrow) and numbered sequentially as it was found. The condition of
all burrow entrances was assessed and the presence or absence of the spider (and
juveniles) at the entrance at night was noted. Burrow diameter was measured to
the nearest mm using a dial caliper (Mitutoyo Co.) and depth was determined to
the nearest cm by inserting a length of rubber into the burrow. In a nearby area,
fifteen burrows were excavated to determine their structure and to collect spiders
for laboratory experiments.

A planimetric map of burrows and other major features in the site was
produced with a telescopic level (Fuji Corp.) and a pair of plane tables. Spot
heights were measured along a series of levelled transects and the contours
interpolated between them were converted to altitudes above sea level using a
Special Survey mark (SSM 3910, 33°01' South, 141°38' East) located within the
site. The distribution of burrows within the site was compared with the values
expected with a low frequency, discrete, random distribution (Poisson) and a
coefficient of dispersion (CD.) was calculated (Sokal & Rohlf 1969).

Rainfall data were obtained from a plastic wedge rain-gauge at the Coombah
Homestead (5 km north of the field site). Solid state temperature sensors
(AD590JH) connected to a 4-channel Rustrak™ recorder (Galton Inc., U.S.A.)
were used to monitor field temperatures for 24 h during each visit. Initially two
sensors were buried at 25 and 60 cm and allowed to equilibrate for 6 weeks. The
temperatures recorded with buried sensors were the same as those from sensors at
similar depths within burrows. Therefore, sensors were buried at the surface, 20
cm and 60 cm for the remainder of the study to determine burrow temperatures.

Spider activity was assessed in terms of the burrow entrance condition (“open”
or “closed”) and the presence or absence of the spider (and any juveniles) in the
top of the burrow at night (“seen” or “not seen”). Evidence of the seasonality of
male mate-seeking activity was obtained from the records accompanying the 16
male specimens of S. stirlingi held in the South Australian Museum, one

KOTZMAN— TARANTULA ACTIVITY PATTERNS

125

Figure 1. — Location and map of the field study site at Coombah (N.S.W.): spider burrows (dots), 1
m contours (solid lines, heights above sea level), roadside fenceline (broken line), buried temperature
sensors (TS) and Special Survey Mark (SSM).

specimen collected at the Coombah Homestead during the study, and the type
specimen from the British Museum (Natural History).

RESULTS

Conditions in the field area. — Daily rainfall records were combined to produce
monthly totals (Fig. 2). Average annual rainfall during the study ranged from
130.0-408.3 mm, with no rain falling in 10 of the 37 months. The rainfall pattern
observed during the study was typical of this region and compared well with
longer-term figures from Menindee (100 km northeast of Coombah) where annual
falls have ranged from 52-766 mm and the mean is 236 mm (Cunningham et al.
1981). At Coombah the mean annual rainfall over the 3 years was 232 mm, and
thus biotic activity related to rainfall (including spider activity) can be considered
typical of the area.

The diurnal temperature ranges were greatest at the soil surface (up to 45° C),
less at 20 cm (typically 5-7° C) and least at 60 cm (no more than 2° C) (Fig. 2).
The trends for annual ranges were the same. Summer temperatures at the surface
were 15-50°C, at 20 cm 25-32° C and at 60 cm around 25-30° C. Winter
temperatures at the surface were 10-30° C, at 20 cm 12-22°C and at 60 cm about
15°C. The slow transfer of heat through the soil caused the maxima and minima
to be reached 6 hours after the surface at 20 cm and 12 hours after the surface at
60 cm. After dawn, the surface temperature generally increased sharply until
noon, whereafter it would oscillate about the maximum until declining steadily
after sunset to a pre-dawn minimum. In the soil, temperatures cycled evenly
between daily maxima and minima.

Burrow characteristics and distribution. — Burrows of S. stirlingi were
unbranched and vertical with somewhat enlarged, horizontal chambers at the base
and total lengths ranging from 31-100 cm. Some were slightly spiralled or gently
curved. Burrow diameter was constant from top to bottom and there was little
silk in the walls. The entrance was circular (diameter 15-27 mm) with a slightly
“trampled” flange, but no turret, door or collar of silk. Occasionally, a thin film
of silk covered the entrance. Although third instar spiderlings raised in the
laboratory constructed small burrows (about 5 mm diameter), none less than 15

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THE JOURNAL OF ARACHNOLOGY

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* — i — r-T — i — I — i — i — T r — i — 1 — i — i — I — i — i — I — I— i — | — i — i — I — i — i — I — i — i — — i — i — I — i — i — 1 — i — )

ONDJ FMAMJ J ASONDJFMAMJ J ASONDJ FMAMJ J ASO

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1984

Figure 2. — Environmental conditions and spider activity at Coombah (N.S.W.). Upper: Monthly
rainfall totals (solid bars) and diurnal soil temperature ranges: temperatures at 60 cm (+/ — 1°C
diurnally) (solid line), temperature ranges at the surface and 20 cm (pairs of vertical lines) and the
temperature range for spider growth (broken lines) (see text). Middle: Adjusted spider activity (see
text); the percentage of open burrows (solid line), burrows in which the occupant was seen (broken
line) and adjusted population size ( N ). Lower: Number of burrows closed for longer than 260 days
indicating spiders lost from the population.

mm diameter was found in the field. Therefore the population which was
monitored consisted of half to fully-grown spiders.

At the conclusion of the study, the site (approximately 81,000 m2) contained
111 marked burrows (mean density = 13.7 burrows/ ha). Analysis of the number
of burrows in each 100 m2 revealed that the distribution was not random x —
45.78, df — 2, p < 0.001), and that they were clumped (C.D. = 2.95) (Sokal &
Rohlf 1969) (Fig. 1). Although burrows were scarce near the claypan, no other
superficial physical features appeared to be correlated with the distribution of
burrows.

There was little correlation between burrow diameter and depth (r2 = 0.11)
(Fig. 3). There appeared to be a positive, linear relationship between burrow
depth and altitude on the lower slopes (i.e., < 51 m), however, burrow depth
appeared to be independent of altitude on the upper slopes (Fig. 4).

Spider activity patterns. — Similar trends of spider activity were observed using
two measures: open burrows and those in which spiders were seen at night. Open
burrows were those in which spiders were active, or those which were neither
plugged by the spider nor closed with sand and debris moved by wind and/or
rain, whether the spider was present or absent. Open burrows in which the
spiders were not seen may have been recently abandoned, or the spider may have
been temporarily out of sight within the burrow. The proportions of spiders seen
were generally 10-20% lower than the proportion of open burrows. Activity was
low in winter (June-July), peaked in spring (September-November) and early fall
(March, April), and was depressed to a variable extent during summer
(December-February). Activity data were expected to be unrealistically high in
the first 10 months as inactive burrows were generally not found, so only the

KOTZMAN— TARANTULA ACTIVITY PATTERNS

127

Figure 3. — Relationship between burrow depth and diameter, Coombah (N.S.W. ( N
r2 = 0. 1 1).

80,

trends of these data were considered. For the remainder of the study, the absolute
percentages of active burrows ranged from 10-85% “open” and 0-75% “seen” As
the total number of burrows monitored increased from 72 to 111, the maximum
activity levels declined throughout the study to 45% “open” and 35% “seen”

Burrows became blocked from the action of natural agents (such as wind and
rain) when the spider did not clear the entrance, or as a result of deliberate
plugging by the spider within the top 10-15 cm of the burrow, or both. When

Figure 4. — Relationship between burrow depth and altitude (mid-point between contours),
Coombah (New South Wales) (N = 80, r2 = 0. 14).

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burrows were closed, there was usually no evidence of the entrance, and it was
generally not possible to determine the cause(s) of closure.

Within 260 days 90.5% of burrows which were inactive became active again. To
estimate the losses from the population (from death or dispersal), burrows which
remained inactive for periods longer than 260 days were considered to be
unoccupied and adjusted activity levels were calculated with the remaining
burrows (Fig. 2). While adjusted activity patterns were essentially the same as
those obtained with the unadjusted population, the maximum levels were higher
at about 90% “open” and 70-80% “seen”, in a population ranging from 54-71
burrows. Apparent losses from the population were not uniformly distributed
throughout the year, but peaked in summer (Fig. 2).

Small spiderlings (instars II IV) were seen in December, February and March,
indicating egg production in spring and summer. Males usually wandered outside
the burrows in March and April (although two were collected as late as June).
Together, these observations suggested that molting occurred in late summer and
mating from summer through winter.

DISCUSSION

Burrow characteristics. — A high correlation between spider size and burrow
diameter has been demonstrated in some burrowing spiders (Decae et al 1982;
Miller & Miller 1984). Petrunkevitch (1911) also suggested that larger spiders
should occupy deeper burrows having had longer to dig them. The burrow depth
of S. Stirling i was independent of burrow diameter (Fig. 3) suggesting that either
variable growth was producing different-aged spiders of similar sizes, or that
other factors, such as soil moisture or texture, affect burrow depth. The increase
in burrow depth with increasing altitude up to 51 m provides circumstantial
support for the potential importance of both soil moisture and texture. The
formation and maintenance of the sand dunes by the action of wind and water
(Bowler 1980) results in the progressive downslope accumulation of clays (Leeper
1964), and potentially an inverse relationship between altitude and soil moisture
owing to the water-holding properties of clays. In addition, calcareous layers may
form within the dune when the water table recedes (Bowler 1980). Meat ants,
Iridomyrmex purpureus (Sm.), whose nests are abundant in this area, penetrate
these layers as a defense against moisture and thermal stresses and to avoid nest
predation (Ettershank 1971). While S. stirlingi may use a similar strategy,
extensive excavation of burrows would be necessary to clarify this possibility.

Burrow blocking behavior. — The closure of burrows at different times of the
year may have different causes. Like other theraphosids, S. stirlingi sometimes
made burrow plugs by combining sand and web (Gertsch 1949; Minch 1979a).
Alternatively, some burrow entrances appeared to become blocked by the natural
accumulation of sand and debris as with the wolf spider Geolycosa wrightii
(Emerton) (Gwynne & Watkiss 1975). Main (1978) and Gray (1968) recorded
door-sealing behavior of trapdoor spiders associated with seasonal weather
conditions and predator avoidance. For S. stirlingi , it seems likely that deliberate
plugging was probably most common in summer (providing protection during
molting and egg production), while natural weathering may have predominated in
winter when spiders were inactive in the cold conditions.

KOTZMAN— TARANTULA ACTIVITY PATTERNS

129

The origin of newly-located burrows is difficult to explain. It seems unlikely
that they were new burrows of spiders already in the population or new adult
recruits from outside the area as there were never sufficient tailings to indicate
excavation of an entirely new burrow. It seems most likely that they were juvenile
recruits which had reached sufficient size to be detected (since no burrows smaller
than 15 mm were found), and/or existing large burrows which had opened after
prolonged periods of closure.

Losses from the population were estimated on the basis of unusually prolonged
or continued burrow closure. Spiders may have died due to old age or disease,
during molting (as often observed in the laboratory), following attack by parasitic
wasps, or they may have dispersed. No evidence was found to suggest that
burrows were vacated in favor of new dwellings. However, if spiders dispersed to
existing burrows, such activity would still have been recorded as a loss. Molting,
mating and production of young in other species of theraphosids are summer
activities (Baerg 1958; Minch 1979b), and adult S. stirlingi maintained in the
laboratory also molted at this time. As the timing of losses coincided with the
production of young at Coombah, it seems likely that mid-summer losses may
have represented the maturation and departure of males for the following
breeding season. Deaths associated with molting would also tend to predominate
in summer.

Spider activity. — The potential for growth can be used to relate activity at the
burrow entrance with temperatures in the soil. In laboratory studies, rates of
growth and development (mediated by food availability) were maximized at 29° C,
decreased linearly from 29-25° C and ceased at and below 20° C (Kotzman 1986).
At 60 cm within the burrow, 20° C was exceeded only from September through
May and 29° C reached only in mid-summer. As the highest levels of activity were
recorded consistently in September and October, the spiders probably exploited
elevated temperatures near the burrow entrance. Humphreys (1974) recorded
almost constant body temperatures in the burrowing wolf spider Geolycosa
goderffroyi (L. Koch) achieved by behavioral thermoregulation. Similar behavioral
adjustment of body temperature in S. stirlingi could facilitate feeding, growth and
development by allowing the spider to optimize its body temperature for these
activities: nocturnal foraging during spring and fall (necessarily near the surface),
feeding (anywhere within the burrow), and molting or egg laying in summer (in
the chamber at the base of the burrow).

The spring peak of open burrows corresponded to the time when the burrow
temperature increased above 20° C and daylength was increasing. Minch (1979b)
claimed that temperature was not the cue for burrow unblocking in
Aphonopelma chalcodes Chamberlin, as spiders at different altitudes (and hence
temperatures) opened their burrows at virtually the same time. In addition, he
observed that spiders maintained in the laboratory blocked their burrows
somewhat later than those in the field, and suggested that . photoperiod or
temperature might at least moderate the behavior. As both temperature and
photoperiod are increasing in spring, it would be difficult to uncouple these
factors under field conditions. While it is possible that annual activity patterns
may be controlled by an endogenous clock set genetically or during early
development (Minch 1979b), it seems more likely that the transition past a
temperature limit (Gabel 1972) regulates burrow-blocking behavior through its
connection with growth processes.

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ACKNOWLEDGMENTS

During this study, the author was supported by a Commonwealth Post
Graduate Research Award. Fiona and Andy McLeod are thanked for use of the
Coombah Station. I would like to thank Dr. David Dunkerley for his assistance
in the field and for designing, building and servicing the temperature monitoring
system. Yael Lubin and John Gross are thanked for their comments on the
manuscript.

LITERATURE CITED

Baerg, W. J. 1958. The Tarantula. University of Kansas Press, Lawrence, Kansas.

Bowler, J. M. 1980. Quanteraary chronology and palaeohydrology in the evolution of Mallee
landscapes. Pp. 17-36, In Aeolian Landscapes in the Semi-arid Zone of South Eastern Australia.
(R. R. Storrier & M. E. Stannard, eds.). Australian Society of Soil Services Inc., Riverina Branch.
Cunningham, G. M., W. E. Mulham, P. L. Milthorpe and J. H. Leigh. 1981. Plants of Western New
South Wales. Published in association with the Soil Conservation Service by the N.S.W. Govt.
Printing Office, Sydney.

Decae, A. E., G. Caranhaac and G. Thomas. 1982. The supposedly unique case of Cryiocorenum
cunicularium (Oliver, 1811) (Araneae, Ctenizidae). Bull. British Arachnol. Soc., 5:410-419.
Ettershank, G. E. 1971. Some aspects of the ecology and nest microclimate of the meat ant,
Iridomyrmex purpureus (Sm.). Proc, Roy. Soc. Victoria., 84:137-152.

Gabel, J. R. 1972. Further observations of theraphosid tarantula burrows. Pan-Pacific EntomoL,
48:72-73.

Gertsch, W. G. 1949. American Spiders. Van Nostrand Co., New York.

Gray, M. R. 1968. Comparison of three genera of trapdoor spiders (Ctenizidae, Aganippini) with
respect to survival under aird conditions. M.Sc. Thesis: University of Western Australia.

Gwynne, D. and J. Watkiss. 1975. Burrow-blocking behaviour of Geoiycosa wrighiii (Araneae:
Lycosidae). Anim. Befaav., 23:953-956.

Humphreys, W. F. 1974. Behavioural thermoregulation in a wolf spider. Nature (Lond.), 251:502-503.
Kotzman, M. 1986. Aspects of the Biology of Selenocosmia stirlingi Hogg (Araneae: Theraphosidae).

Ph.D. Thesis: Monash University, Australia.

Leeper, G. W. 1964. Introduction to Soil Science. Melbourne University Press, London.

Main, B. Y. 1964. Spiders of Australia. Jacaraeda Press, Australia.

Main, B. Y. 1978. Biology of the arid-adapted Australian trap-door spider Anidiops viilosus
(Rainbow). Bull British Arachnol. Soc., 4:161-175.

Miller, G. L. and P. R. Miller. 1984. Correlations of burrow characteristics and body size in burrow
wolf spiders (Araneae, Lycosidae). Florida. EntomoL, 67:314-317.

Minch, E. W. 1979a. Burrow entrance plugging behaviour in the tarantula Aphonopelma chalcoides
Chamberlin ((Araneae: Theraphosidae). Bull. British Arachnol. Soc., 4:414-415.

Minch, E. W. 1979b. Annual activity patterns in the tarantula Aphonopelma chalcodes Chamberlin.
Novit. Arthropod., 1:1-34.

Peck, W. B. and W. H. Whitcomb. 1970. Studies on the biology of a spider Chiracanthium indusum
(Hentz). Arg. Exp. Sta., Div. Agr. Univ. Arkansas Bui. no. 753, 76 pp.

Petrunkevitch, A. 1911. Sense of sight, courtship and mating in Dugesieiia hentzi (Girand) a
theraphosid spider from Texas. Zool. Jahrb. Abt. Syst. Geogr. Oekol. Tiere, 3:355-375.

Sokal, R. R. and F. J. Rohlf. 1969. Biometry, W. H. Freeman & Co., San Francisco.

Stradling, D. J. 1978. The growth and maturation of the ‘Tarantula”, Avicularia avicularia L. Zool. J.
Linn. Soc., 62:291-303.

Turnbull, A. L. 1962. Quantitative studies of the food of Linyphia triangularis Clerck (Araneae;
Linyphiidae). Canadian EntomoL, 94:1233-1245.

Turnbull, A. L. 1965. Effects of prey abundance on the development of the spider Agelenopsis potted
(Blackwell) (Araneae: Agelenidae). Canadian EntomoL, 97:141-147.

Manuscript received January 1989, revised June 1989.

Capocasale, R. M. 1990. Las especies de la subfamilia Hippasinae de America del Sur (Araneae,
Lycosidae). J. Arachnol, 18:131-141.

LAS ESPECIES DE LA SUBFAMILIA HIPPASINAE
DE AMERICA DEL SUR (ARANEAE, LYCOSIDAE)

Roberto M. Capocasale

Instituto de Investigaciones Biologicas Clemente Estable
Division Zoologia Experimental
Ave. Italia 3318, Montevideo, Uruguay

ABSTRACT

Nine species of the sixteen that comprise the Hippasinae indicated for South America are studied.
Allocosa brasiliensis (Petrunkevitch, 1910) n. comb. {= Moenkhausiana brasiliensis Petrunkevitch =
Araucaniocosa difficilis Mello-Leitao n. syn.) is redescribed and the data of the habitat where it
occurs is reported. The taxa of G lies c hie lla Mello-Leitao are considered “ species inquirendo ”. They
should be better placed into Allocosa. Hogna birabenae (Mello-Leitao, 1941) n. comb. ( = Birabenia
birabenae Mello-Leitao) is not redescribed completely. Birabenia taeniata Mello-Leitao, 1943 is
considered “ species incerta ” because the holotype is juvenile (it should be a Tetragonophthalma ,
Pisauridae). Although Sosippus nitidus (Mello-Leitao, 1944) n. comb. ( = Hippasella nitida Mello-
Leitao) is not redescribed (its holotype is damaged), it is being studied. All taxa are transferred into
three subfamilies: Allocosinae, Lycosinae and Sosippinae.

RESUMEN

Se estudian nueve de las dieciseis especies que comprenden las Hippasinae indicadas para America
del Sur. Se redescribe Allocosa brasiliensis (Petrunkevitch, 1910) n. comb. ( = Moenkhausiana
brasiliensis Petrunkevitch = Araucaniocosa difficilis Mello-Leitao n. syn.) y se dan datos sobre el
habitat donde vive. Los taxones de Glieschiella son considerate s como “ species inquirenda ”, y mejor
ubicados bajo Allocosa. Hogna birabenae (Mello-Leitao, 1941) n. comb. ( = Birabenia birabenae
Mello-Leitao) se redescribe fragmentariamente. Birabenia taeniata Mello-Leitao, 1943 se considera
“ species incerta ”, debido a que el holotipo es un ejemplar juvenil (seria una Tetragonophthalma ,
Pisauridae). Se estudia Sosippus nitidus (Mello-Leitao, 1944) n. comb. ( = Hippasella nitida Mello-
Leitao) aunque no se describe porque el holotipo esta muy deteriorado. Todos los taxones se
redistribuyen en tres subfamilias: Allocosinae, Lycosinae y Sosippinae.

INTRODUCCION

Bonnet (1961) enumera para Lycosidae las siguientes subfamilias: Hippasinae
Simon, 1898, Pardosinae Simon, 1898, Lycosinae Bertkau, 1878, Cyclocteninae
Simon, 1898 y Bradystichinae Simon, 1884. Esta subdivision fue adoptada, entre
otros, por Roewer (1954, 1959, 1960) en cuyos trabajos estan indicadas casi todas
las Lycosidae de America del Sur.

La subfamilia Hippasinae este representada en America del Sur por los
siguientes taxa: Porrimosa diversa (Pickard-Cambridge), Porrimosa glieschi
(Mello-Leitao), Porrimosa seccurifera (Tullgren), Porrimosa callipoda (Mello-
Leitao), Porrimosa lagotis (Holmberg), Porrimosa harknessi (Chamberlin),

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•n

Figuras 1-5. — Allocosa brasiliensis (Petrunkevitch); 1, tarso del palpo izquierdo del macho, ventral;
2, apofisis mediana (A. difficilis Mello-Leitao, tipo, MNRJ, Chile, Maullin); 3, apofisis mediana (M.
brasiliensis Petrunkevitch, lectotipo, PMNH, Brasil, Ypiranga); 4, epigino, ventral; 5, espermatecas
(MHNM, Uruguay, Marindia).

Porrimosa castanea (Mello-Leitao), Hippasella nitida Mello-Leitao, Birabenia
birabenae Mello-Leitao, Birabenia taeniata Mello-Leitao, Moenkhausiana
brasiliensis Petrunkevitch, Moenkhausiana argentinensis Mello-Leitao,
Glieschiella halophila Mello-Leitao, Glieschiella senex Mello-Leitao, G lies c hie lla
alticeps Mello-Leitao, Araucaniocosa difficilis Mello-Leitao.

Dondale (1986) definio Lycosidae sobre la base de tres sinapomorfias: (a) ojos
dispuestos de manera peculiar, (b) tibia del palpo en los machos sin apofisis
retrolateral y (c) madres que transportan activamente las ootecas en las hileras y
las arahitas jovenes sobre su abdomen. Asimismo subdividio la mencionada
familia tambien en cinco subfamilias: Sosippinae Dondale, 1986, Venoniinae
Lehtinen e Hippa, 1979, Allocosinae Dondale, 1986, Pardosinae Simon, 1898 y
Lycosinae Simon, 1898.

En el sistema de este autor, obviamente, se cambian las denominaciones, pero
ad e mas la agrupacion de los generos es diferente a la de Roewer. La esencia de la
diferencia se halla en que, Roewer, desestimo el valor diagnostico del cymbium y
del epigino, mientras que Dondale se baso en la morfologia de los organos
genitales. Hoy, practicamente, existe consenso entre los especialistas de la familia
sobre que, la clasificacion de Roewer, esta apoyada en criterios que no responden
totalmente a la realidad. (En efecto, no pude comprobar, en el examen de un
numero signficativo de tipos de especies de America del Sur, la constancia de los
caracteres genericos usados por Roewer. La mayoria de las especies revisadas por
mi, las cuales dicho autor ubico en los generos redefinidos por el, no “entraron”
en esos generos).

Ante esta situation considere conveniente adecuar las Lycosidae de esta parte
del Continente, a los conceptos de Dondale. La finalidad de mi proyecto fue, en
una primera etapa, integrar las especies de Hippasinae de America del Sur a una
clasificacion sistematica mas objetiva que la de Roewer.

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133

Este articulo informa los resultados de esa investigacio, ia cual reubica los
miembros de Hippasinae de America del Sur en 3 subfamilias, segun fueron
definidas por Dondale (1986).

Metodos de presentation. — Abreviaturas: MLP, Museo de La Plata, Argentina;
MNRJ, Museu Nacional de Rio de Janeiro, Brasil; CAS, California Academy of
Sciences, San Francisco, USA; MZUC, Museo de Zoologia, Universidad de
Concepcion, Chile; PMNH, Peabody Museum of Natural History, Yale
University, USA; MRCN, Museu Riograndense de Ciencias Naturais, Porto
Alegre, Brasil; MNHM, Museo de Historia Natural de Montevideo, Uruguay; a,
atrium am, apofisis mediana; amt, apofisis mesial del tegulum; at, apofisis
terminal; c, conductor; E, espermateca; e, embolo; t, tegulum.

Los valores meristicos estan dados en milimetros, significando: extremes;
media ± desviacion tipica (ejemplares medidos).

Salvo indication, las descripciones estan basadas en mas de 10 ejemplares
conservados en alcohol.

Subfamilia Allocosinae

Allocosa brasiliensis (Petrunkevitch, 1910) nueva combination
Figuras 1-7, Mapas 1-2

Moenkhausiana brasiliensis Petrunkevitch, 1910: 223, figs. 26-29; 1911: 569; Bonnet, 1957: 2971.
Araucaniocosa difficilis Mello-Leitao, 1951:328, fig. 1; Casanueva, 1980: 22, figs. 17-19 (in part,
identificacion erronea); Brignoli, 1983: 438. Sinonimo nuevo.

Glieschiella sp.: Capocasale, 1982: 3.

Glieschiella halophila: Dondale, 1986: 331.

Diagnosis. — Especie distribuida en el Sur de America del Sur. Habita espacios
abiertos, suelos arenosos y costas de rios y lagunas. Hace agujeros en el suelo que
recubre interiormente con tela. La coloration general del cuerpo es amarillo muy
palido (mimetiza con la arena). Los machos tienen la “palea” muy desarrollada,
la apofisis mediana del palpo es bifida, una rama es puntiaguda la otra roma,
curvada y canaliculada. Las hembras carecen de “septum” mediano y de “atrium”,
las espermatecas son bulbosas y sin nodulo. La longitud corporal en ambos sexos
cubre extremos entre 1 1-20 mm.

Description. — Macho : Cuerpo: largo total 11.9-19.6; 14.24 ± 4.67 (13);
cefalotorax: largo 6.0-9.8; 8.05 ± 1.00 (13); ancho: 5.0-8.1; 6.14 ± 1.00 (13);
castano-amarillo; area ocular: castano-rojo manchada de castano oscuro;
margenes: castano-oscuro. Esternon: castano-rojo (en algunos ejemplares amarillo
palido). Queliceros: castano-rojo. Patas: femures: I, 4.7 — 8.5; 6.48 ± 1.14 (13); II,

4.3— 7.7; 6.09 ± 0.96 (13); III, 4.0— 8.2; 5.97 ± 1.07 (13); IV, 5.0— 9.8; 7.25 ±
1.39 (13); amarillos; basitarsos: castano-rojo. Abdomen: amarillo palido con
manchas negras dorsalmente; puntuaciones negro lateralmente; -amarillo palido
ventralmente. Palpos: “cymbium” con una apofisis mediana bifida, una rama
corta y puntiaguda la otra curvada ventralmente canaliculada (Figs. 2, 3); “palea”
desarrollada; apofisis terminal corta, aguda, poco visible.

Membra : Cuerpo: largo total 11.2 — 14.7; 13.41 ± 1.38 (14); cefalotorax: largo
6.0— 8.0; 6.81 ± 0.95 (14); ancho 4.6— 7.1; 5.26 ± 0.87 (14). Femures: I, 4.1-7.2;
5.71 ± 0.85 (14); II, 4.0— 6.3; 5.28 + 0.86 (14); III, 3.7— 6.5; 5.37 ± 0.87 (14); IV,

4.4— 8.6; 6.59+ 1.10(14).

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Figura 6. — Marindia (Uruguay) habitat de Allocosa brasiliensis (Petrunkevitch). Las flechas indican
los lugares donde generalmente se encuentra la especie.

La hembra cromaticamente es muy semejante al macho. Epigino: sin “septum”
ni “atrium”; espermatecas bulbosas, sin nodulos; tubos copulatorios cortos (Figs.
4, 5).

Distribucion. — (Maps. 1, 2) Sur del Brasil, Sur-Oeste de Uruguay y centro de
Chile.

Habitat. — Espacios abiertos y suelos arenosos de las costas de rios y lagunas.
Este habitat tiene amplias variaciones de temperature durante el dia debido a que
la vegetacion es escasa y practicamente no hay sombra (Fig. 6).

Figura 7. — Agujeros hechos por un ejemplar
inmaduro de Allocosa brasiliensis (Petrunkevitch).
La fotografia muestra la estructura de los agujeros
los cuales tienen 2 entradas cerradas; ambos
agujeros se comunican.

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135

Mapas 1,2.- 1, Distribucion conocida de Allocosa
brasiliensis (Petrunkevitch); 2, Sector de America
del Sur indicado en el mapa 1.

El porcentaje de humedad relative es alto por la proximidad de las fuentes de
agua, la velocidad de las corrientes de aire es baja a nivel del suelo.
Cuantitativamente el componente biologico predominante son las hormigas.

Desde el punto de vista ecologico, este habitat corresponderia a lo que Elton y
Miller (1954) denominaron como: “Aquatic-terrestrial system”.

Un lugar fisico en el cual se resumen las caracteristicas estructurales del habitat
(donde es muy frecuente hallar a A. brasiliensis ) es El Pinar (Uruguay). Se dan a
continuation los datos de los factores bioticos y abioticos obtenidos en dicho
lugar, en noviembre (1988) (epoca de alta actividad de la especie) a las 1900 horas
(“instante climatologico medio”): Vegetation herbacea predominante: Senecio sp.
y Panicum sp. Mesofauna a nivel del suelo: Tetragonoderus sp. (Coleoptera)
Tronistes sp. (Coleoptera), Labidura sp. (Dermaptera), Acromyrmex sp.
(Hymenoptera), Liolaemus sp. (Lacertilia, Iguanidae). Temperature (grados
Celsius): a m. 0.10 por debajo del suelo, 22.6°, a nivel del suelo, 19.10°, a m.l
sobre el suelo, 19.4°; Humedad Reiativa: a nivel del suelo, 98%, a m.l sobre el
suelo, 96%. Velocidad de las corrientes de aire (millas por hora): a nivel del suelo
3, a m.l sobre el suelo, 11.

Agujeros. — Los adultos de A. brasiliensis cavan bajo la superficie del suelo,
agujeros mas o menos verticales, que recubren interiormente de tela, de una
profundidad que puede llegar a los 10 cm. Algunas veces se puede ver, en
estudios experimentales, que ejemplares inmaduros cavan agujeros de 3 a 6 cms,
con 2 entradas cerradas cuyas 2 ramas convergen en un agujero simple (Fig. 7).

Comportamiento constructor de refugios. — El comportamiento constructor de
refugios, es esencial en el cavado de agujeros; es muy estereotipado. Para su
estudio y considerando el tema con extrema sencillez, puede ser desintegrado en 6
unidades comportamentales: busqueda; giro de 90 grados; cavado/ toma de
piedras; deposit©; sellado; giro de 180 grados.

Las partes anatomicas que la arana utiliza en cada unidad de comportamiento
son: en la de busqueda las patas I y II; en la de cavado/ tomo de piedras los
queliceros y pedipalpos; en la de sellado las hileras.

Comentarios. — Del analisis del “cymbium” del tipo de Araucaniocosa difficilis
conclui que es coespecifico con el lectotipo de Moenkhausiana brasiliensis. La
apofisis mediana y la apofisis terminal son semejantes en los tipos de ambas
especies. La cantidad de dientes internos en los queliceros y las medidas del area

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ocular tambien son semej antes. For supuesto, como M. brasiliensis es un ejemplar
joven existen diferencias en el tamano. Como regia general podria establecerse
que, cuanto mayor es un ejemplar, la apofisis mediana mas se parece al esquema
de la figure 2.

El analisis de dichos caracteres agregado a los datos ecologicos disponibles me
condujo a la conclusion que, Moenkhausiana y Araucaniocosa son sinonimos
recientes (“junior synonyms”) de Allocosa.

Roewer (1954, 1959) y Brignoli (1983) indicaron 14 especies de Allocosa para
America del Sur. Yo no estimo que todas esas especies puedan ser ubicadas alii
aplicando el concept© actual de este genera, (por ejemplo ni Allocosa mutillata
(Mello-Leitao) ni Allocosa paraguayensis (Roewer) pertenecen a dicho geeero).
De acuerdo con la lectura de las descripciones especificas, estableci como
hipotesis de trabajo que, Allocosa podria ser dividido formalmente en 2 grupos:
el grupo Allocosa funerea y el grupo Allocosa brasiliensis . Pero antes de sacar
concln.sion.es. sera necesario revisar cada uno de los tipos de las especies para
fundamentar factualmente los grupos mencionados. (Esta carencia hizo que me
abstenga de hacer una diagnosis diferencial para A. brasiliensis).

Si se analiza la figure 18 del articulo de Casanueva (1980) se comprueba que
fue cometido un error. Ni el epigino ni las espermatecas son como en A. difficilis.
Al examinar los ejemplares estudiados por Casanueva (1980) concha que
pertenecen a una Lycosinae. De acuerdo con el nivel actual de mis conocimientos
en la familia no la pude identificar aun.

Los datos ecologicos obtenidos en el habitat tienen significacion sistematica,
Estoy de acuerdo con Brady (1979: 174) quien juzga que esta clase de
informacion es tan util al sistematico como la relacionada con las caracteristicas
morfologicas. En el habitat donde se halla A. brasiliensis hay ausencia total de
aranas de otras familias. Por tal razon, estimo que la estructura de ese ecosistema
es un caraeter diagnostic© importante que debe usarse tambien desde el punto de
vista sistematico.

Ejemplares examinados. — Veinte ejemplares identificados por Casanueva como A, difficilis de
CHILE: Temuco, 20 km E Temuco, 7 Ene. 51 (Ross, Michaelbacher), 4 hembras, 2 machos, 3
juveniles (CAS), identification erronea; Temuco, 25 km E Temuco, invierno 51 (M. Smith), 1 juvenil
(CAS); Bio Bio, Negrete, 29 Ene. 51 (Ross, Michaelbacher), 8 juveniles (CAS); Osorno, 20 km E.
Puyehue, 26 Ene. 51 (Ross, Michaelbacher) 1 macho (CAS), identification erronea; Lapihue, sea coast
of P. Montt, 21 Ene. 51 (Ross, Michaelbacher) 1 hembra (MZUC). Un ejemplar identificado por
Mello-Leitao, Maullm, 1 macho (MNRJ) tipo. Un ejemplar identificado por Petrunkevitch como
Moenkhaausiana brasiliensis de BRAZIL: Ypiranga (Moenkhause), 1 macho (PMNH) lectotipo, sensu
Lise. Ochenta y dos ejemplares identificados por el autor de URUGUAY: Montevideo, Pajas Blancas,
27 Ene. 1980 (Gudynas), 1 macho (MHNM); Paysandu, 11 Oct. 1976 (Capocasale, Bruno), 2 hembras,
2 machos (CAS); Canelones, Marindia, 8 Abr. 1976 (Capocasale, Costa), 15 hembras, 15 machos
(MHNM); Canelones, Marindia, 8 Die. 1975 (Costa, Urruty), 2 machos, 1 inmaduro (CAS),
Canelones, Las Toscas, 2 Mar. 1941 (Robayna), 2 hembras (MHNM); Soriano, Santo Domingo, 19
Ene. 1977 (Bonino), 1 hembra (MHNM); Soriano, Isla Pepe Ladron, 17 Ene. 1977 (De Sa), 1 macho
(MHNM); Rio Negro, Isla Barrientos. Feb. 1977 (Olazarri), 1 hembra, 1 macho (MHNM); Colonia,
Nueva Palmira, 6 Die. 1970 (Capocasale), 2 machos, 5 inmaduros (CAS); Colonia, Punta Gorda, 26
Feb. 1968 (Capocasale, Bruno), 1 hembra, 1 inmaduro (MHNM); Colonia, Playa de la Agraciada, 6
Set. 1958 (Bonino), 1 macho (MHNM); Rocha, Laguna Negra, 16 Feb. 1976 (Blengini), 1 hembra
(MHNM); Rocha, Cabo Polonio, Feb. 1976 (Capocasale), 1 macho (CAS); Rocha, Parque Santa
Teresa, Die. 1977 (Costa), 10 hembras, 6 machos, 2 juveniles (MHNM); San Jose, San Gregorio, 4
Set. 1966 (Morey), 1 hembra (MHNM) Maldonado, Laguna del Sauce, 29 Ago. 1976 (Costa, Urruty),
1 hembra, 3 machos (MHNM); Maldonado, Punta Colorado, 8 Feb. 1978 (Aleman), 2 machos
(MHNM); Maldonado, ruta 10, Km 112, 25 Die. 1975 (Capocasale), 1 macho (CAS).

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137

Species incerta. — Moenkhausiana argentinensis Mello-Leitao, 1938:99, f. 14. Un
ejemplar de Argentina: Rio Negro, Isla Tehuel Malal (tipo inmaduro) examinado,
depositado en el MLR

Glieschielle Mello-Leitao

Species inquirenda. — Como actualmente solo examine 2 de los 3 tipos de este
genero, solo tengo los siguientes comentarios respecto de sus miembros.

Glieschiella alticeps Mello-Leitao, 1944: 347, f. 37-38. Dos ejemplares de
Argentina, San Bias (sintipos, 1 macho; 1 hembra, inmaduros) examinados,
depositados en el MLP. En el MNRJ hay 2 ejemplares adultos (paratipos, 1
macho; 1 hembra) examinados, sobre la base de los cuales, seguramente,
Mello-Leitao hizo su descripcion. (Considero esta especie valida).

Glieschiella halophila Mello-Leitao, 1932: 69; 1943 a: 161, f. 19. (No halle el tipo
de esta especie que estaria depositado en el MNRJ. El Dr. A. Lise me informo
(com. pers.) que es un ejemplar inmaduro. Dondale (1986) senalo:
“ Moenkhausiana (type: Moenkhausiana brasiliensis Petrunkevitch, 1910). . . the
generic name is a senior synonym of Glieschiella Mello-Leitao, 1932 (type:
Glieschiella halophila Mello-Leitao, 1932)”. (No discuto esa conclusion. De
acuerdo con esta y segun la sinonimia anotada anteriormente por mi, todas las
especies de Glieschiella pasarian al genero Allocosa).

Glieschiella senex Mello-Leitao, 1945: 254. Un ejemplar de Argentina, Entre
Rios, Colon, (tipo, hembra) examinado, muy deteriorado, depositado en el
MLP. (El examen del “cymbium”, que pude recuperar a pesar del estado del
ejemplar, confirmaria mi hipotesis que pertenece a Allocosa. Considero esta
especie sinonima).

Subfamilia Lycosinae

Hogna birabenae (Mello-Leitao, 1941) nueva combinacion
Figuras 8~1 1

Birahenia birabenae Mello-Leitao, 1941: 137, figs. 27, 33, 34; Roewer, 1954: 310; 1960: 1005, Brignoli,
1983: 432.

Diagnosis.— Es poco practice, dado el estado en que estan los ejemplares, dar
una diagnosis de esta especie basandose en la observacion de los 4 ejemplares
utiles, actualmente disponibles.

Descripcion. — (ver Comentarios). Macho : Cuerpo: largo total 11.3 (1);
cefalotorax: largo 5.4 (1); ancho 4.3 (1). Palpos como en las figuras 8 y 9.

Hembra : Cuerpo: largo total 9.7 — 12.3 (2); cefalotorax: largo 4.5 — 5.6 (2);
ancho 3.2 — 3.8 (3). Epigino y espermatecas como en las figuras 10 y 11. (Otros
caracteres ver Mello-Leitao, 1941: 137).

Distribucion. — Norte y centro de la Republica Argentina.

Comentarios. — En el Museo de La Plata estan depositados los unicos cinco
ejemplares (tipos) disponibles (un macho, tres hembras, adultos, una hembra
inmadura). Todos estan muy deteriorados; los miembros, el cefalotorax y el

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Figuras 8-11. — Hogna birabenae (Mello-Leitao); 8, tarso del palpo izquierdo del macho, ventral; 9,
apofisis mediana (B. birabenae Mello-Leitao, alotipo, MLP, Argentina, Tucumae); 10, epigino,
ventral; 1 1, espermatecas ( B . birabenae Mello-Leitao, tipo, MLP, Argentina, La Rioja).

abdomen se hall an separados. A pesar de lo anterior es posible ubicar
genericamente la especie b as an dose en el examen de la genitalia, el eual permite
condui t que pertenece al genero Hogna .

El lamentable estado en que estan los tipos y paratipos de esta especie, in hi be
hacer una redescripcion satisfactoria. El procedimiento para identificar la especie,
que solucioearia esta deficiencia, sen a consultar la description de Mello-Leitao
(1941: 137) completandola con los datos y figuras dados en este trabajo.

Las diagnosis de Mello-Leitao (1941) y de Roewer (1959) no coinciden con las
coeclusiones que se sacan luego de examinar los tipos. De acuerdo con esas
conclusiones y luego de considerar todos los generos de Lycosieae establecidos
por Roewer, se estaria ante un genero nuevo. Yo prefer! no seguir esa tinea de
razonamiento por las razones expuestas en la Introduction.

Ejemplares exarninados. — Cinco ejemplares identificados por Mello-Leitao como Birabenia
birabenae de ARGENTINA: Tucuman, Banado (Biraben), 1 macho (MLP) alotipo; La Rioja,
Sanogasta (Biraben), 2 hembras, 1 hembra inmadura (MLP); Santa Fe, Vera, 1 hembra (MLP).

Species incerta. — Birabenia taeniata Mello-Leitao, 1943: 108, fig. 9. Un ejemplar
de Argentina, Cordoba, Bell Ville (tipo, inmaduro) examinado, depositado en el
MLR (El examen de los dientes internes de los queliceros y de los ojos dio que
se pod via tratar de una especie de Tetragonophthalma — Pisauridae— -).

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139

Figuras 12, 13. — Sosippus nitidus (Mello-Leitao) tarso del palpo izquierdo del macho; 12, ventral;
13, lateral externa (S', nitidus Mello-Leitao, tipo, MLP, Argentina, La Plata).

Subfamilia Sosippinae
Porrimosa Roewer

Comentarios. — Las conclusiones sobre las especies del genero Porrimosa fueron
tratadas en un articulo anterior (Capocasale 1982); se pueden resumir en dos
grupos:

Especies incerta. — Porrimosa diver sa (Pickard-Cambridge) (tipo inmaduro),
Porrimosa glieschi (Mello-Leitao) (tipo inmaduro), Porrimosa securifera
(Tullgren) (tipo inmaduro), Porrimosa callipoda (especie descripta
incompletamente; tipo perdido).

Especies seguras. — Porrimosa lagotis (Holmberg), Porrimosa harknessi
(Chamberlin) (descripto solo el macho), Porrimosa castanea (Mello-Leitao)
(descripta solo la hembra).

Sosippus nitidus (Mello-Leitao, 1944) nueva combination
Figuras 12-13

Hippasella nitida Mello-Leitao, 1944: 343, fig. 32; Roewer, 1954: 313.

Comentarios. — Hoy, el unico ejemplar disponible, en coleccion es el tipo y esta
considerablemente deteriorado. Es imposible ubicar las patas y otras partes del
cuerpo, dado que estan separadas, excepto un trozo del ceralotorax y un
pedipalpo. Son las unicas partes rescatables. Esto me inhibe de diagnosticar
genero y especie, asi como redescribir la ultima.

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No obstante, a pesar del pesimo estado de conservation de este ejemplar, el
examen del trozo del cefalotorax que contiene el 70% aproximadamente del area
ocular, indico que es similar a la diagnosis que dio Brady (1962) para Sosippus .
Asimismo el tarso del pedipalpo carece de “palea” y de apofisis terminal, Todo lo
cual lleva a concluir que, este ejemplar, pertenece a Sosippus.

Hippasella, por lo tan to, es un sinonimo nuevo de Sosippus .

Ejemplares examinados. — Ue ejemplar ideetificado por Mello-Leitao de ARGENTINA: La Plata
(Biraben), 1 macho (MLP) tipo.

AGRADECIMIENTOS

A R. Arrozpide (MLP), A. Timotheo Da Costa (MNRJ), W. Pulawski (CAS),
T. Cekalovic (MZUC), C. L. Remington (PMNH) por el prestamo de ejemplares,
a A. Lise (MRCN) por el envio de los dibujos del holotipo de M. brasiliensis , a
C. S. Carbonell, L. C. de Zolessi y E. Morelli por la identification de insectos, a
J. Rovner, C. Dondale y revisores anonimos, quienes hicieron importantes
sugerencias al primer manuscrito de este articulo,

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Roewer, C. 1954. Katalog der Araneae von 1758-1954. Institut royal des Sciences naturelles de
Belgique. 2a: 1-923. Bruxelles.

Roewer, C. 1959. Exploration du Parc National de 1’U pemba. Araneae, Lycosaeformia II.

(Lycosidae). Institut des Parcs Nationaux du Congo Beige. 1-518. Bruxelles.

Roewer, C. 1960. Exploration du Parc National de FUpemba. Araneae, Lycosaeformia II.

(Lycosidae). Institut des Parcs Nationaux du Congo Beige. 519-1040. Bruxelles.

Manuscript received June 1988, revised July 1989.

Marshall, S. D. and G. W. Uetz. 1990. Incorporation of urticating hairs into silk: A novel defense
mechanism in two Neotropical tarantulas (Araneae, Theraphosidae), J. Arachnol., 18:143-149.

INCORPORATION OF URTICATING HAIRS INTO SILK:

A NOVEL DEFENSE MECHANISM IN TWO NEOTROPICAL
TARANTULAS (ARANEAE, THERAPHOSIDAE)

Samuel D. Marshall1

and

George W. Uetz

Department of Biological Sciences, M. L. #006
University of Cincinnati
Cincinnati, Ohio 45221 USA

ABSTRACT

Two species of New World theraphosid; Theraphosa leblondi from French Guiana, and
Megaphobema sp. from Ecuador incorporate abdominal setae into silk constructs. Theraphosa
incorporates setae into the egg sacs and the silk mats on which they molt. Megaphobema sp. includes
them in the egg sacs only. The setae used in the egg sacs by both these spiders are from the lateral
region of the abdomens, the setae which Theraphosa uses in the silk mat are from the lateral and
posterior regions. All abdominal regions tested on Theraphosa had urticating hairs present. To test the
possible benefits of this behavior, the egg sacs and silk mats were tested for urticarial effect. The egg
sacs failed to elicit any urticarial response in either humans or two species of mouse (Mus musculus
and Peromyscus sp.). Egg sac material with or without setae was found to be an effective barrier to
the larvae of the fly Megaselia scalaris. The silk mats of T. leblondi were found to be more effective at
stopping the movement of M. scalaris larvae than theraphosid silk which lacked them.

INTRODUCTION

Urticating setae have been well documented in both the larval and adult instars
of lepidopterous insects, particularly those in the family Saturniidae. The
urticating setae of the Lepidoptera are known to employ either a chemical
urticant, mechanical irritation, or both (Goldman et al 1960; Pesce and Delgado
1971). Mygalomorph spiders in the family Theraphosidae have also been known
to possess urticarial setae (Bates 1836), but only recently has the phenomenon
been examined (Cooke et al. 1972; Cooke et al. 1973).

Cooke et al. (1972) examined specimens in museum collections and described
four basic urticating hair types in New World theraphosids (Old World tarantulas
apparently lack them). In contrast to the urticating setae of the Lepidoptera, the
urticating hairs of tarantulas rely on mechanical irritation alone. These setae are
characterized by a penetrating end (which may be at the proximal or distal end),
with fine barbs located along the point and longer barbs along the shaft. The
base of the hair has a constriction which serves as a break-off point. Tarantula

'Present address: Graduate Program in Ethology, Department of Zoology, University of Tennessee,
Knoxville, Tennessee 37996 USA.

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defensive hairs are concentrated on the posterior region of the abdomen, although
there is an exception to this in the genus Ephehopus (Marshall and Uetz 1990).
Most tarantulas possess a suite of behaviors which accompany defensive hair
shedding. These may be stridulating, rearing and striking with the first two pairs
of legs, and attempting to bite. The hairs are shed by rapid downward strokes of
one or both of the fourth legs with the ventral surface of the tibia being applied
to the posterior abdomen.

Two tarantula species; Theraphosa leblondi Latreille (1804) from French
Guiana, and Megaphobema sp. Pocock (1901) from Ecuador (adult male and
female specimens have been deposited in the collection of the Queensland
Museum, Brisbane, Australia) have been observed to incorporate lateral
abdominal setae into their egg sacs. Additionally, captive Theraphosa have been
observed to shed hairs onto the silk mat upon which they molt. The phenomenon
of incorporating urticating hairs into silk constructs has also been noted for
Avicularia sp. in Trinidad, which apparently include the hairs in their retreats for
defense against predators (A. Bordes in Cooke et al. 1972). In this study we
investigate the defensive use of urticarial hairs by Theraphosa ; their distribution
on the abdomen, and their incorporation into shedding mats and egg sacs.

METHODS

Specimens of Theraphosa and their egg sacs were collected in the field in
French Guiana between 1981 and 1988, and egg sacs were also collected from the
laboratory colony. The specimens of Megaphobema were collected in the vicinity
of Puerto Misuali, Ecuador in December of 1984. The shedding mats were
collected from the cages of recently molted Theraphosa and stored for later use.
Megaphobema has not been observed to make such mats.

To investigate the range of distribution of urticating hairs on the abdomen of
Theraphosa , a comparative survey of hairs on three regions (lateral, dorsal, and
posterior) of the abdomens of five preserved specimens was made. The lateral
area was chosen as it was the region from which the hairs were shed for the egg
sac, the dorsal area because it is a region not known to be associated with any
hair shedding behavior, and the posterior area as it is the site of the hairs used in
defense. A 1.0 mm square sample of cuticle was dissected out of each site from
each specimen and the hairs were scraped off onto a microscope slide and
dispersed in a drop of mounting medium by stirring with a probe. Four regularly
spaces, parallel transects were taken across the slide and all the hairs were
counted and classified as urticating or non-urticating.

The pubescence of the egg sacs of both Theraphosa and Megaphobema is
obvious to the unaided eye. Scanning electron micrographs were prepared of
Theraphosa egg sac material for closer examination of the structure of the silk-
hair matrix. To examine the composition of hairs in the egg sac material, 1.0 mm
square samples were taken from five egg sacs. The silk-hair matrix was teased
apart, mounted on a slide and the two hair types counted in total. The inclusion
of hairs into the shedding mats was measured by taking a 2.0 mm square sample
from five shedding mats produced by captives. The material was shredded and
dispersed in mounting medium as with the egg sacs. The hairs were counted and
classified in total.

MARSHALL & UETZ— SETAE USE IN SILK BY THERAPHOSIDS

145

To test the urticarial action of the egg sac material against predators, studies
were conducted on three vertebrate species, and one invertebrate species. The
effect of the egg sac material on humans was tested by rubbing an egg sac against
the underside of the forearms of three human volunteers. This was seen as
adequate, since the human response to the defensive shedding of posterior
abdominal hair by Theraphosa is immediate and strong. The shed hairs are borne
up on air currents, resulting in a burning, itching sensation on exposed skin
surfaces and in the upper respiratory tract. In a test of the egg sac material’s
effect on a small vertebrate predator model, six wild-caught deer mice
(. Peromyscus sp.) were used. A sample of egg sac material was applied to the
mouths of restrained individuals by holding a piece in a forceps and rubbing it
around the mouth-nose area, after which the mouse was returned to its cage and
observed for fifteen minutes. In both these tests, any inflammation or behavioral
evidence of itching was considered a positive response.

To test for the effect of ingesting hairs, a 1.0 cm square sample of egg sac
material was shredded and incorporated into 30.0 gm of peanut butter and
offered to the deer mice. A second test was performed to examine the
effectiveness of intact egg sac material in deterring vertebrate predation. Samples
of material from Theraphosa egg sacs were used to enclose the ends of two 10.0
cm by 3.5 cm cylindrical plastic vials that were baited with peanut butter. White
laboratory mice (Mus musculus) were used. The mice were tested in two groups
of five. First, they were fed peanut butter to accustom them to the smell and
taste, and then they were fasted for six hours, having free access to water, after
which they were offered the tubes (one to a group).

A phorid fly occurs in association with Theraphosa in French Guiana
(Marshall, pers. obs.). This species belongs to the genus Megaselia, and is
undescribed (W. H. Robinson pers. comm.). Adult flies have been observed on
the spiders in both the field and captivity; the late instar larvae are seen on the
cephalothorax and femora, and puparia were found affixed to the
cepahlothoracic apodeme and the femora. As this fly is the only known parasite
of Theraphosa (other than an unidentified mite) a congeneric phorid ( Megaselia
scalaris) was selected to test the deterrent effect of the silk-hair constructs. The
flies were trapped from a laboratory cricket colony. M. scalaris is a common
scavenger, and freely oviposits on dead animal material. Material from two field
collected Theraphosa and one captive-produced Brachypelma smithii Simon
(1891) egg sac was used to enclose the ends of patent-lip vials baited with dead
crickets. Brachypelma was used as it does not include hairs in the egg sac. One
vial capped with fine nylon mesh was used as a control. These seven vials were
placed in a cage with approximately 60 flies.

The shedding mats were also tested using larval Megaselia scalaris . The ability
of these larvae to move about on the shedding mats was compared to the total
distance travelled on non-pubescent silk matting laid down by captive Avicularia
sp. from French Guiana (this silk had been examined for setae and none were
found). The trials were run for 10 minutes.

RESULTS

Both field-collected and captive-produced Theraphosa egg sacs are pubescent in

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Figures 1, 2. — SEM of Theraphosa egg sac material: 1, the outer covering of hair; 2, a close-up with
a Type III urticating hair indicated by the arrow.

appearance. The scanning electron micrographs revealed that the egg sac material
is covered with a mixture of the long, non-urticarious body hairs and the smaller
urticarious hairs (Figs. 1, 2). The much larger non-urticarious hairs are the most
obvious, despite the numerical dominance of the urticating hairs. In the process
of making the egg sac, the female Megaphobema and Theraphosa denude the
lateral regions of their abdomen (Figs. 3, 4). This behavior is in contrast to the
shedding of posterior abdominal hairs during defensive displays. While
Megaphobema egg sacs were not microscopically examined, a captive specimen of
Megaphobema was observed in the process of producing an egg sac. The female
begin by laying down a circular mat of silk within the retreat by standing in the
center and turning around. The spider would then pause and shed the hairs with
slow, downward stroking motions of the fourth tarsal scopula against the lateral
areas of the abdomen. Alternate sides were used between bouts of hair shedding.
The behavior is similar to preening in both tempo and use of the tarsal scopulae.

Figures 3, 4. — Megaphobema sp. females before (3), and after (4) production of an egg sac. The
denuded lateral regions of the abdomen are visible in 4, indicated by an arrow.

MARSHALL & UETZ— SETAE USE IN SILK BY THERAPHOSIDS

147

Table 1. — Two-way ANOVA on the proportion of urticating hairs on the dorsal, lateral, and
posterior abdominal regions of five females of Theraphosa leblondi.

F ratio

Regions

1669.91

834.96

25.47

P« 0.005

Specimens

296.62

74.16

2.62

P>0.1

Error

262.24

32.78

Total

2228.77

While egg-laying behavior has never been observed in Theraphosa , it is assumed
to be the same.

In the samples taken from Theraphosa abdomens, urticating setae were found
at all sites sampled, and were the numercially dominant type. The percent
urticating hairs among the setae on the dorsal region of the abdomen was 87.0 ±

3.0 (mean ± one standard deviation); the lateral 74.0 ± 0.06; and the posterior

95.0 ± 7.0. The urticating hairs were all what Cooke et al. (1972) refer to as type
III (V. Roth, pers. comm.). The urticating hairs from the posterior abdomen were
longer, ranging from 0. 5-1.0 mm. In the other two sites sampled, the hairs were
approximately 0.1 mm.

A two-way ANOVA testing variation between sites and between spiders was
performed using the arc-sine transformed proportion of urticating hairs. The
difference between the sites was significant, but not between spiders (Table 1).
When the proportion of urticarial hairs in the egg sac material and the lateral
abdomen were compared using a Mann-Whitney U test, the results were not
significantly different. The five egg sacs had 66.0 ± 2.0 percent urticating hairs. In
the five shedding mats both the long posterior and short lateral urticating hairs
were mixed, and together comprised 86.0 ± 4.0 of the total hairs. Taken
separately, the long urticating hairs constituted 24.0 ± 14.0, and the short
urticating hairs were 63.0 ± 17.0.

In the tests for an urticarial response to egg sacs applied to the skin, no itching
was reported by the human volunteers. Mice did not appear distressed nor did
they indulge in excessive grooming behavior after similar exposure.

In the first feeding test, all the peanut butter-egg sac material mixture was
consumed. Microscopic examination of the feces revealed both urticating and
non-urticating hairs had been ingested and passed through, and the mice
appeared normal. In the second feeding test, using intact material, the results
were similar. The mice initially investigated the tubes, sniffing and nibbling at the
material, and then ignored them. The tubes were left in the cages overnight, and
15 hours later, the egg sac material had been chewed and partially consumed,
along with a portion of the peanut butter. There were no egg sac fragments in the
cage, and it was mostly gone from the tubes. Examination of the feces once again
revealed that the hairs (and silk) had been ingested and passed through without
adverse effects.

The phorid experiment was terminated after 72 hours when the adult flies were
dead. The flies had oviposited on the control vial (with the mesh on top), one
Brachypelma vial and one Theraphosa vial. Larvae were observed in the control
vial only. The Theraphosa shedding mats were more effective at slowing the
progress of the phorid larvae (mean distance in mm travelled in 10 minutes ± one
standard deviation: Theraphosa mats, 8.8 + 6.8; Avicularia webbing, 42.0 ± 33.5;

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t = 2.17, df = 8, p = 0.06). All the phorid larvae on the Theraphosa webbing
eventually stopped. On the Avicularia webbing, three stopped, one left the
webbing, and one continued moving for the duration of the trial. The greater
variability of the distance travelled by the control group resulted in a greater
sample variance, which is responsible for the marginal significance value.
Examination with a dissecting microscope revealed that on Avicularia silk the
setae of the larval flies which stopped had become entangled in the loose silk
strands. The phorid larvae on the Theraphosa shedding mats were likewise
observed under magnification and seen writhing around, coated with Theraphosa
hair, having anchored themselves with their posterior appendages.

DISCUSSION

The tarantulas of the New World have evolved a unique defensive strategy
utilizing urticating setae, which is a characteristic shared only with the
Lepidoptera. The variety of hair types and apparent uses indicates the utility of
such an adaptation. Why it is only found in the New World theraphosid fauna,
however, remains a mystery.

No egg sac predators of Theraphosa have ever been recorded. As this is a little-
studied species, this does not preclude their existence. It is obvious that both
Theraphosa and Megaphobema are making an investment in both time and
energy, as well as in paying the possible costs that shedding a complete coating of
hairs may confer (i.e., loss of boundary layer effects, parasite defense).

Until we know more about the predators and parasites of Theraphosa there
may be no way to know what selective forces induced the evolution of the unique
behaviors leading to the inclusion of setae in egg sacs. However, evidence from
experimental studies reported here allows some speculation about possible
selective agents.

The vertebrate tests indicate that the silk-hair matrix has no negative effect on
three mammalian species (although these species have no previous ecological or
evolutionary exposure to theraphosid spiders). In its egg sacs Theraphosa uses a
field of hairs that contains the lowest proportion of urticating hairs, and a hair
type that is distinct from those used in individual defense against vertebrates.
These findings argue against a hypothesis that this defensive mechanism is
adapted to deter vertebrate predators. Additionally, during incubation, both
Theraphosa and Megaphobema guard their egg sacs constantly and with vigor.
This behavioral investment may be considerable, as Theraphosa in captivity
attend the egg sac for 1 1 weeks until hatching (Marshall pers. obs.). As female
Theraphosa will engage in typical defensive displays while holding the egg sac in
their fangs, it seems likely that an attack by a large, vertebrate egg sac predator
would be warded off at an early stage in the predatory sequence, or the female
herself would be the target of attack. The tests with Megaselia scalaris larvae
indicate that egg sac material with or without setae may be an effective barrier to
penetration by larval parasitoids or scavengers. However, the behavior of M.
scalaris larvae on the Theraphosa shedding mats indicates that the incorporated
hairs function as a means of deterring parasites. During the molting process a
spider is clearly more vulnerable to boarding (or re-boarding) by ectoparasites.
On at least one occasion, a captive Theraphosa was seen to have a later instar

MARSHALL & UETZ— SETAE USE IN SILK BY THERAPHOSIDS

149

Megaselia sp. larvae moving about on one of its patellae as the spider prepared to
molt. It is also noteworthy that while both Theraphosa and Megaphobema
include setae in the egg sacs, only the species known to have the phorid
ectoparasite spins a shedding mat which includes setae. This adds credence to the
hypothesis that combining urticating hairs with silk is an adaptation against
larval dipteran parasitoids.

ACKNOWLEDGMENTS

We wish to thank R. Raven and W. Robinson for identification of the spiders
and flies, respectively; also the numerous people who have been of indispensable
help in the field (in chronological order) A. Miles, G. Tavakilian, M. Modde, J.
Lapp, Thomas, la famille Scolard, and S. Doumain. The senior author especially
wishes to thank the Marshall family for their support and toleration of a
Theraphosa colony in their basement during the early stages of his tarantula
studies.

LITERATURE CITED

Bates, H. 1836. A Naturalist on the River Amazons. John Murray, London.

Cooke, J., V. Roth and F. Miller. 1972. The urticating hairs of theraphosid spiders, Amer. Mus.

Novitates. No. 2498:1-43.

Cooke, J., F. Miller, R. Grover and J. Duffy. 1973. Urticaria caused by tarantula hairs. Amer. J.
Trop. Med. Hygiene, 22(1): 130-133.

Goldman, J., F. Sawyer, A. Levine, J. Goldman, S. Goldman, and J. Spinanger. 1960. Investigative
studies of skin irritation from catepillars. J. Investigative Dermatol., 34:67.

Marshall, S. D. and G. W. Uetz. 1990. The pedipalpal brush of Ephebopus sp. (Araneae,
Theraphosidae): evidence of a new site for urticating hairs, Bull. Br. Arachnol. Soc., 8(4): 122-124.
Pesce, H. and A. Delgado. 1971. Poisoning from adult moths and caterpillars. Pp. 119-156. In
Venomous Animals and Their Venoms. (W. Bucherl and E. Buckley, eds.). Academic Press, New
York.

Manuscript received June 1989, revised September 1989.

Tsurusaki, N. and J. C. Cokendolpher. 1990. Chromosomes of sixteen species of harvestmen
(Arachnida, Opiliones, Caddidae and Phalangiidae). J. ArachnoL, 18:151-166.

CHROMOSOMES OF SIXTEEN SPECIES OF HARVESTMEN
(ARACHNIDA, OPILIONES, CADDIDAE AND PHALANGIIDAE)

Nobuo Tsurusaki

Department of Biology, Faculty of Education
Tottori University, Tottori 680 Japan

and

Janies C. Cokendolpher

2007 29th Street, Lubbock, Texas 79411 USA

ABSTRACT

Chromosomes of Caddo agilis (Caddidae) and fifteen species of Phalangiidae were investigated. In
three species, Nelima satoi , N. simiiis, and Eumesosoma roeweri , presence of XY-XX (male
heterogametic) sex chromosome system was newly ascertained. On the other hand, ZW-ZZ (female
heterogametic) sex chromosome system was suggested to be present in Mitopus morio. Effeminate (2n
= 20) and normal (2n = 18) males of Protolophus tuberculatus were found to differ in chromosome
number. A survey of known records of chromosome numbers in Caddidae and Phalangiidae revealed
a general trend that the number is greater in both Caddidae (2n = 30) and Phalangiinae (2n = 20-36),
fewer in Gagrellinae (2n = 10-22), and intermediate in Leiobuninae (2n = 16-26). Evolutionary trends
are briefly discussed and compared with those in other arachnids.

INTRODUCTION

Studies on chromosomes of harvestmen are few with the counts of only 36
species being reported (Tsurusaki 1986). Chromosomal observation has, however,
great importance in gaining comprehensive understanding of geographic
variation, speciation process, and phylogeny of Opiliones, since chromosomes of
harvestmen often vary among related species and sometimes among geographical
populations within the same species (e.g., genus Leiobunum : Suzuki 1976a;
Tsurusaki 1985a, b).

To advance our general knowledge of opilionid chromosomes, we have prepared
chromosome slides over the past seven years. This paper is the result of this study
and describes chromosomes of fifteen species of Phalangiidae and one species of
Caddidae.

MATERIALS AND METHODS

Sources of the specimens are listed in Table 1 and in the appendix.
Chromosome preparations were prepared from testes or ovarian tissues of young
adults and penultimates. Air-dried slides were made principally according to the
method described in Tsurusaki (1985a) for the species from Japan and the

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Table 1. — A list of materials used in the present study and obtained results. Detailed collecting data
are given in the Appendix. M = male(s), F — female(s), juv. = juvenile(s). 2n chromosome number in
parentheses denotes value inferred from haploid number alone. For distinction of the geographic
forms of Melanopa grandis, see text.

Species

Locality

No. indiv.

obs.

2n chrom.

number

M F

No.

modal

cell

(M/F)

Caddo agilis

HOKKAIDO:Nopporo

9 juv. (F)

—

Mitopus morio

Is. Rishiri

3 juv.(2M, IF)

9/3

Homolophus arcticus

HOKKAIDO: Wakasakanai

3 juv. (M)

—

Homolophus rishiri

Is. Rishiri

2 juv. (M)

—

Phalangium opilio

IDAHO:Moscow

1 M

—

Dalquestia formosa

TEXASiCenter Point

1 M

—

Nelima satoi

EHIMEiMt.Ishizuchi

2 juv. (F)

—

FUKUOKA: Mt.Hiko

1 juv. (M)

—

Nelima similis

NAGANO:Takat6

4 M

—

Leiobunum flavum

TEXAS:L.Stubblefield

4 M

Leiobunum townsendi

TEXAS:Concho Co.

1 M

Eumesosoma roeweri

TEXAS:Concho Co.

2 M, 2F

3/2

TEXAS:Kerrville

1 M

—

Protolophus tuberculatus

CALIFORNIA:San Anselmo

1M (1983)

(20)

—

CALIFORNIA:San Anselmo

1 M (1984)

—

Protolophus sp.

CALIFORNIA:Little

Sycamore Canyon

2 M

—

Trachyrhinus rectipalpus

TEXAS:Tilden

1 M

—

Melanopa grandis Form 1

NAGANO:L.Misuzu

1 juv. (M)

imSSE

Form 1

NAGANO:Mt.Kirigamine

1 juv. (M)

—

Form 2

TOTTORLMt.Daisen

3 M

—

Form 3

FUKUOKA:Mt.Hiko

3 M

Form 3

Is. Tsushima: Hidakatsu

1 M

—

Form 1

Is.Tsushima:Mt.Ariake

1 M

—

Paraumbogrella pumilio

HOKKAIDO:Sunagawa

1 M

—

method in Cokendolpher and Brown (1985) for the species from the U.S.A. Of
these methods, the procedures of the former were slightly modified in
preparations after 1984 as follows: (1) use of Ringer’s solution at the first step
was abandoned and specimens were directly dissected in hypotonic solution. The
tissues were removed and transferred to the same solution on another depression
slide for hypotonic treatment; (2) as the hypotonic solution, 0.1% sodium citrate
with colchicine (19 parts of 1% sodium citrate to one part of 0.1% colchicine
solution) was used instead of pure 1% sodium citrate.

Metaphase chromosomes were serially arranged according to descending order
of length (Figs. 1-3, 8-11, 18-24, 29-33). When a pair of heteromorphic
chromosomes were observed only in either sex, those were considered as sex
chromosomes. Haploid idiograms of each species were drawn based on a somatic
metaphase plate with the clearest chromosome configurations by calculating
percent ratios of length for each chromosome to the total length of the haploid
chromosomes (TCL). TCL is the total of lengths of all haploid autosomes and
one sex chromosome (X or Z) when detected. These idiograms should be
considered as tentative since good metaphase spreads were scarce and results are
based on only one or a few chromosomal spread(s). Nevertheless, they served to
obtain rough compositions of karyotypes. Classification of chromosomal

TSURUSAKI & COKENDOLPHER— CHROMOSOMES OF HARVESTMEN

153

1 li it tl ! ^ || II 9 «• »* n

ii «* •« •• *

z z

Figures 1-3. — Karyotypes of Caddo agilis and Mitopus morio : 1, Caddo agilis, female (2n = 30); 2,
3, Mitopus morio (2n = 32); 2, female; 3, male. Scale = 5 pm.

morphology was made according to Levans et al. (1964), where chromosomes are
classified into the following five categories: metacentric (1.0 i r < 1.67),
submetacentric (1.67 ^ r < 3.0), subtelocentric (3.0 Si r <7.0), acrocentric (7.0 <
r Si °°) and telocentric, (r = °°). r L/S, where L and S are lengths of long arm
and short arm, respectively.

RESULTS
Family Caddidae

Caddo agilis Banks. — 2n (female) = 30 (Figs. 1, 4). Chromosomes were
surveyed for females collected in 1982 from Nopporo, Hokkaido. A tentative
idiogram based on some representative karyotypes (Fig. 1) is shown in Fig. 4.
Chromosomes in which presence of short arm is unclear were prevalent in smaller
ones; and chromosomes No. 9 or Nos. 13-15 were suggested to be telocentric or
acrocentric. This species is considered to be parthenogenetic and only three males,
one from North America and two from Japan, have been found (Gruber 1974;
Suzuki and Tsurusaki 1983). The two males from Japan were collected in 1979 at
Nopporo. However, no male has been found since then, so chromosomes of
males of this species remain unknown.

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THE JOURNAL OF ARACHNOLOGY

o 10

^ 0J

Bqddd

10 H i—

10- C

BSSBBbsbsL

z w

10-

X X

Figures 4-7. — Idiograms of Caddo agilis and three species of Phalangiidae: 4, Caddo agilis, female;
5, Mitopus morio, female; 6, Homolophus arcticus, male; 7, Dalquestia formosa, male.

Family Phalangiidae
Subfamily Phalangiinae

Mitopus morio Fabricius. — 2n (male, female) = 32 (Figs. 2-3, 5). This
conforms to the number reported by Sokolow (1930) based on specimens from
westernmost area of European part of U.S.S.R and by Jennings (1982) on
specimens from northern England. Only one cell from a female (Figs. 2, 5)
provided a chromosomal spread acceptable for karyotype analysis. The karyotype
seems to consist of 15 pairs of autosomes and one heteromorphic pair of
chromosomes. Compared with a chromosome spread from the male (Fig. 3),
chromosomes of this heteromorphic pair appeared to be sex chromosomes and
correspond to Z and W chromosomes. Z chromosomes are the largest and
metacentric, whereas W is metacentric and similar in size to chromosome No. 7.
Autosomes are metacentric except for Nos. 3 an 12 which are submetacentric.

Homolophus arcticus Banks. — 2n (male) = 24 (Figs. 6, 8). No sex
chromosomes were detected. The karyotype consisted of only metacentrics (Nos.
4, 5, 7-9, 12) and submetacentrics (others). In this respect, chromosome
composition of this species is similar to that of M. morio.

TSURUSAKI & COKENDOLPHER— CHROMOSOMES OF HARVESTMEN

155

s M)iu u ti uiiuiiiiiiti

M .1 m

° M IMMI n MO •«

Figures 8-11. — Karyotypes of males of four species of Phalangiidae: 8, Homolophus arcticus (2n =
24); 9, Homolophus rishiri (2n = 24); 10, Phalangium opilio (2n = 32); 11, Dalquestia formosa (2n =
22). Scale = 5 jum.

Homolphus rishiri Tsurusaki. — 2n (male) = 24 (Figs. 9, 12). This 2n number
is the same as H. arcticus . Further analysis was not possible due to the indistinct
chromosomal spread (Fig. 9). Numerous first meiotic metaphases showed 12
bivalents without exception (Fig. 12).

Phalagium opilio Linneaus. — 2n (male) = 32 (Fig. 10). Only one
spermatogonial metaphase plate, which is not enough for detailed karyotype
analysis, could be found; it showed 2n = 32 clearly (Fig. 10). This number
corresponds to that reported by Sokolow (1930) who studied the population in
westernmost area of European U.S.S.R. However, this number does not agree
with Juberthie (1956), who reported 2n = 24 for specimens from Moulis, Ariege,
France. Further survey is needed to confirm whether this incongruence in
chromosome number means a different species.

Subfamily unnamed

For comments on the placement of the genus Dalquestia Cokendolpher, see
Cokendolpher (1984).

Dalguestia formosa (Banks). — 2n (male) = 22 (Figs. 7, 11). No sex
chromosomes were detected. Karyotype consists of four pairs of submetacentrics
(Nos. 2, 3, 6, 9) and seven pairs of metacentrics (others).

Subfamily Leiobuninae

Nelima satoi Suzuki. — 2n (male, female) = 16 (Figs. 18, 19, 25). The
karyotype is composed of seven pairs of autosomes and one pair of male
heterogametic sex chromosomes (male: XY, female: XX) (Figs. 18, 19).
Autosomes are metacentric except for two pairs (Nos. 5, 7) being submetacentric

156

THE JOURNAL OF ARACHNOLOGY

Figures 12-17. — Meiotic chromosomes in males: 12, Homolophus rishiri, metaphase I (n = 12); 13,
Dalquestia formosa, metaphase I (n = 1 1); 14, Melanopa grandis (Mt. Ariake, Is. Tsushima),
metaphase I (n = 10); 15, 16, Protolophus tuberculatus\ 15, metaphase I (n = 10); 16, metaphase II (n
= 9); 17, Protolophus sp., metaphase I (n = 11). Scale = 5 jxm,

(Fig. 25). The X chromosome is the second largest submetacentric, and Y is
submetacentric similar in size to the shortest chromosome No. 7.

Nelima similus Suzuki. — 2n (male) = 20 (Figs. 20, 26). The karyotype
consisted of nine pairs of autosomes and one pair of heteromorphic sex
chromosomes (Fig. 20). Autosomes are comprised of two pairs of submetacentrics
(Nos. 2, 5) and seven pairs of metacentrics (others) (Fig. 26). The metacentric X
and Y chromosomes are, respectively, the largest and the shortest.

Leiobunum flavum Banks. — 2n (male) — 22 (Figs. 21, 27). The karyotype
consisted of three pairs of submetacentrics (Nos. 4, 6, 8) and eight pairs of
metacentrics (others). No sex chromosomes were discernible. This number, 2n =
22, is the same as those reported in four species of Leiobunum C. L. Koch of
North America (Parthasarathy and Goodnight 1958; Tsurusaki and Holmberg
1986).

Leiobunum townsendi Weed. — 2n (male) = 20 (Fig. 22). Only one
spermatogonial metaphase plate with 20 chromosomes was obtained (Fig. 22).
Detailed karyotype is unknown.

TSURUSAK1 & COKENDOLPHER— CHROMOSOMES OF HARVESTMEN

157

H H \ 1| •? If >1

X Y

*% it

X X

20 IAaAM UK *« 3 A ** U

X V

Kim <4 St I* SA At

AS t> SA

22^C*U #» «%«*

<( )»tt«l «« till a< it ** )<

X X

Figures 18-24. — Karyotypes of five species of Leiobuninae: 18, 19, Nelima satoi (2n = 16); 18, male,
Mt. Hiko; 19, female, Mt. Ishizuchi; 20, Nelima similis (2n = 20), male; 21, Leiobunum flavum (2n =
22), male; 22, Leiobunum townsendi (2n = 20), male; 23, 24, Eumesosoma roeweri (2n = 22); 23,
male; 24, female. Scale = 5 jam.

Eumesosoma roeweri (Goodnight and Goodnight). — 2n (male, female) = 22
(Figs. 23, 24, 28). The autosomes were composed of ten pairs of metacentrics
(Fig. 28). The X chromosome is a metacentric similar in size to chromosome No.
2; while Y is a submetacentric and somewhat smaller than X.

Subfamily Sclerosomatinae (?)

For the tentative placement of the genus Protolophus Banks, to which the
following two species belong, in this subfamily, see Cokendolpher (1985). Large
series of Protolophus spp. from various localities in the southwestern U.S.A.

158

THE JOURNAL OF ARACHNOLOGY

20-

Figures 25-28. — Idiograms of males of four species of Leiobuninae: 25, Nelima satoi ; 26, Nelima
similis; 27, Leiobunum flavum ; 28, Eumesosoma roeweri.

reveal the presence in many populations of two types of males: a larger, more
robust type and a smaller, effeminate type. This type of dimorphism is rare in
harvestmen. The differences in the pedipalps are dramatic, with normal males
often having femora twice as thick as those of effeminate males of the same
population. One of us (J.C.C.) has thought for many years that these differences
were due to a different number of molts for the two forms to reach adulthood.
Attempts to rear Protolophus spp. in the laboratory (by J.C.C.) have failed, but
successful copulations have been observed between single females and both types
of males.

Protolophus tuberculatus Banks. — 2n (male) = 18 and 20 (Figs. 15, 16, 29),
Two males (one normal, one effeminate) collected from the same locality in San
Anselmo, California but in different years, respectively 1983 and 1984, were used
for chromosome observation. The result reveals the two forms have different
chromosome numbers. That is, the effeminate male collected in the summer of

TSURUSAKI & COKENDOLPHER— CHROMOSOMES OF HARVESTMEN

159

.lltttltJ MMMM

XX ,x ZXhK ^

•• •<«- ti «♦ » ♦,

II IM Sioll ■

Figures 29-33. — Karyotypes of males of four species of Sclerosomatinae and Gagrellinae: 29,
Protolophus tuber culatus (2n = 18); 30, Protolophus sp. (2n = 22); 31, Trachyrhinus rectipalpus (2n
= 10); 32-33, Melanopa grandis (2n — 20); 32, Lake Misuzu; 33, Hidakatsu, Is. Tsushima. Scale = 5
jum.

1983 showed n = 10 (hence it is expected to be 2n = 20) in its first and second
meiotic metaphase plates (Fig. 15), whereas the normal male from sampling in

1984 showed chromosome number 2n — 18 and n = 9 (Figs. 29 and 16). Detailed
karyotype of the latter is unknown, although most of the chromosomes seem to
be submeta- or metacentric. Further study, including females, is needed to
understand the implication of this discrepancy in chromosome number.

Protolophus sp. — 2n (male) = 22 (Fig. 30). Only one spermatogonial
metaphase spread with 22 chromosomes was obtained. Detailed composition of
chromosomes is unknown, although most chromosomes seem to be metacentric
or submetacentric (Fig. 30). Since this species could not be identified, we are
depositing the specimen in the collection of the California Academy of Sciences,
San Francisco.

32 II l| I* O

33 5a -» vin m

Subfamily Gagrellinae

Trachyrhinus rectipalpus Cokendolpher. — 2n (male) = 10 (Figs. 31, 34). The
karyotype consists of three pairs of metacentric (Nos. 1-3), one pair of
submetacentric (No. 4), and one pair of small acrocentric chromosomes (Figs. 31
and 34). No sex chromosomes were detected. This chromosome number, 2n = 10,
is the lowest reported in Opiliones, ranking with Systenocentrus japonicus Hirst
and Paraumbogrella pumilio (Karsch) (Tsurusaki 1982; also see below).

Melanopa grandis Roewer. — 2n (male) = 20 (Figs. 32, 33, 35). Chromosomes
were surveyed for specimens from six localities which represent three different
geographic forms defined as follows in terms of structure of male palpi (P) and
female genital operculum (GO) (cf. Suzuki 1972).

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THE JOURNAL OF ARACHNOLOGY

10-

n n 35

x x n

Figures 34-35. — Idiograms of males of two species of Gagrellinae: 34, Trachyrhinus rectipalpus ; 35,
Melanopa grandis.

Form /: male with normal but robust P and female with three (sometimes two)
-sectioned GO [figs. 1(6-8) and 3IJK].

Form II: male with robust P having trigger-shaped tibiae; female with two-
sectioned GO [figs. 1(9) and 3H].

Form III: male with normal and slender P; female with unsectioned GO [figs.
1(5) and 3E in Suzuki, 1972].

In spite of the prominent geographic variation in external morphology,
numbers of chromosomes were determined to be 2n = 20 (n = 10) without
exception. Chromosomes of this species were generally so small in size (2.2 jum
on average) that few chromosome spreads could be analyzed in detail. Of these,
representative karyotypes from Lake Misuzu, Nagano Pref. (Form I) and
Hidakatsu on Is. Tsushima (Form III), and an idiogram based on the former are
shown in Figs. 32, 33 and 35, respectively. The karyotype consisted of five pairs
of metacentrics (Nos. 1, 6-8, 10), four pairs of submetacentrics (Nos. 3-5, 9), and
one pair of subtelocentrics (No. 2). No sex chromosomes were detected.

Paraumbogrella pumilio (Karsch). — 2n (male) = 10. On the basis of specimens
from Sapporo, Hokkaido, Tsurusaki (1982) reported chromosomes of this species
as 2n (male, female) — 10 and XY (male) - XX (female) in its sex chromosome
constitution under the name P. huzitai Suzuki (see Suzuki 1985, for the name
change). This time, a male collected from Sunagawa, which is located about 70
km northeast of Sapporo, was chromosomally examined. Although no
chromosome spreads sufficient for analysis could be obtained, chromosome
number was clearly counted as 2n = 10.

TSURUSAKI & COKENDOLPHER— CHROMOSOMES OF HARVESTMEN

161

DISCUSSION

Table 2 is a compilation of the number of chromosomes and sex chromosome
system so far recorded of various opilionid species, belonging to Caddidae and
Phalangiidae. A comparison at subfamllial level reveals that chromosome
numbers tend to be greater In Caddinae, Caddidae (2n = 30) or Phalangiinae (2n
= 20-36), fewer in Gagrellinae (2n = 10-22), and intermediate in Leiobuninae (2n
= 16-26).

However, chromosome number often fluctuates within the genus, sometimes
even within a species (e.g., Leiobunum montanum Suzuki: Tsurusaki 1985b). This
forms a contrast with the situation in most spiders where the chromosome
numbers are relatively stable at the familial level (Hackman 1948; Suzuki 1954;
Datta and Chatterjee 1983). Difference in population structure between both
groups of animals may partly explain this disparity. That is, probability that
newly emerged chromosomal variants are fixed in a population may be relatively
high in opilionids due to their low vagility which promotes inbreeding and drift.
On the other hand, in spiders, inbreeding and drift would be unlikely to occur,
since ballooning would facilitate both dispersal of the sibs and gene flow among
populations. Consequently, even if a chromosomal mutation did occur within a
population of spiders, the prospect that this mutant would predominate existent
chromosomes would be low. Thus, karyotype evolution in spiders is expected to
be conservative. Such correlation between population structuring and
evolutionary rate of karyotypic evolution is found in various animal groups and
is also theoretically supported (White 1978; Bush 1981).

On the other hand, in spite of great diversity in number of chromosomes, both
meta- and submetacentrics overwhelmingly predominate in the component
chromosomes of Opiliones, compared to telo- or acrocentrics (Figs. 4-7, 25-28,
34, 35; of, also Tsurusaki 1985b). This fact suggests that Robertsonian
translocation is not a main cause for the change of chromosome number.
Further, this also makes a contrast with the situation in spiders where
chromosomes are usually structured as telo- or acrocentrics (Hackman 1948;
Suzuki 1954; Kageyama et al. 1978; Kageyama and Seto 1979). Primary factors
for the difference in chromosome structure between the two groups are still
incompletely known.

Sex chromosome composition in Opiliones has been determined as usually XY
XX (male heterogametic) based on Paraumbogrella pumilio and some species of
Leiobunum (Tsurusaki 1982, 1985a, b; Tsurusaki and Holmberg 1986). In
addition to these species, Nelima satoi , N. similis , and Eumesosoma roeweri were
also revealed to have the same system of sex chromosomes in the present study.
On the other hand, presence of female heterogamety with ZW (female) - ZZ
(male) was suggested in Mitopus mono. It deserves attention, since no species
with female heterogamety has hitherto been recorded in arachnids (White 1973;
Bull 1983: 17). There Is a possibility that this sex chromosome system
predominates In species of Phalangiinae, since (1) we failed to detect any
heteromorphic sex chromosomes in males of the other species of Phalangiinae
examined in this work and (2) female heterogamety is also suggested in
Oligolophus aspersus (Karsch), one of the relatives of M. morio (N. T unpubl).
Further survey using material of both sexes of various species is needed. Other

162

THE JOURNAL OF ARACHNOLOGY

Table 2. — Number of chromosomes and sex detrmination in various species of opilionids belonging
to families Caddidae and Phalangiidae. M = male, F = female. 2n chromosome number in
parentheses denotes the one inferred from haploid number alone. References are abbreviated as
follows: 1, Jennings (1982); 2, Juberthie (1956); 3, Parthasarathy and Goodnight (1958); 4, Sharma
and Dutta (1959); 5, Sokolow (1930); 6-12, Suzuki (1941, 1957, 1966, 1976a, 1976b, 1980, 1986); 13,
Tomohiro (1940); 14-16, Tsurusaki (1982, 1985a, 1985b); 17, Tsurusaki and Holmberg (1986); NT,
Tsurusaki unpubl.; PS, Present study.

Species

Locality

Sex

chrom.

number

Type of

sex

determ.

Refer.

Family Caddidae

Caddo agilis Banks

Japan: Hokkaido,
Nopporo

Family Phalangiidae

Subfamily Phalangiinae

Olioglophus aspersus Japan: various

(Karsch) localities

M,F

ZW(?)

6, NT

Oligolophus tridens
(C. L. Koch)

U.S.S.R.:

Leningrad

—

Mitopus mono

(Fabricius)

U.S.S.R.:

Leningrad

—

England:
northern part

Japan: Is. Rishiri

M,F

Mitopus ericaeus

Jennings

England:

northern part

—

Opilio parientinus
(De Geer)

U.S.S.R.:

Leningrad

—

Homolophus arcticus
Banks

Japan: Hokkaido

—

Homolophus rishiri
Tsurusaki

Japan: Is. Rishiri

—

Phalangium opilio
Linnaeus

U.S.S.R.:

Leningrad

(32)

—

France

—

U.S.A.: Idaho,

Moscow

Rilaena triangularis U.S.S.R.:

(Herbst) Leningrad

(= Platybunus triangularis : in ref. 5)

(36)

—

Subfamily unnamed

Dalquestia forrnosa

(Banks)

U.S.A.: Texas

—

Subfamily Leiobuninae

Nelima satoi Suzuki Japan

M,F

Nelima similis Suzuki

Japan: Nagano

Pref.

Leiobunum japanense
japonicum (Suzuki)

Japan

TSURUSAKI & COKENDOLPHER— CHROMOSOMES OF HARVESTMEN

163

Leiobunum japonicum

japonicum Miiller

Japan

M,F

6,17

Leiobunum paessleri
Roewer

Canada:

British Columbia

Leiobunum crassipalpe
Banks

U.S.A.:

details unknown

Leiobunum nigripes

Weed

U.S.A.:

details unknown

Leiobunum vent-
ricosum Wood

U.S.A.:

details unknown

22(?)

Leiobunum flavum

Banks

U.S.A.:

Texas

Leiobunum townsendi
Weed

U.S.A.:

Texas

Leiobunum rupestre

(Herbst)

U.S.S.R.:

Leningrad

Leiobunum hikocola
Suzuki

Japan: Kyushu,

Mt. Hiko

Leiobunum montanum
Suzuki

Japan: various
localities

M,F

18-26

9.16

Leiobunum hiasai

Suzuki

Japan: Yamanashi
Pref.

(24)

Leiobunum sadoense

Tsurusaki

Japan: Is. Sado

(18)

Leiobunum kohyai

Suzuki

Japan: Honshu

9,15

Leiobunum hiraiwai
(Sato and Suzuki)

Japan: various
localities

M,F

18-22

7, 11, NT

Leiobunum curvipalpe
Roewer

Japan: various
localities

M,F

7, NT

Eumesosoma roeweri

(Goodnight and
Goodnight)

U.S.A.:

Texas

M,F

Subfamily Sclerosomatinae (?)

Protolophus U.S.A.:

tuberculatus Banks California

18,(20)

Protolophus sp.

U.S.A.:

California

—

Subfamily Gagrellinae

Trachyrhinus

rectipalpus

Cokendolpher

U.S.A.:

Texas

Gagrellopsis nodulifera
Sato and Suzuki

Japan:

Hiroshima Pref.

Gagrellula ferruginea

(Loman)

Japan: various
localities

M,F

10-22

6, 12, NT

Melanopa grandis

Roewer

Japan: various
localities

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THE JOURNAL OF ARACHNOLOGY

Melanopa unicolor

Roewer

India

. —

Systenocentrus
japonicus Hirst

Japan

(10)

Paraumbogrella
pumilio (Karsch)

Japan: Hokkaido

14, PS

than these, Parthasarathy and Goodnight (1958) suggested the presence of XO-
XX (male heterogametic) system in opilionids based on their observation on
Vonones sayi (Simon) (= V ornata : in their paper) of family Cosmetidae
(suborder Laniatores). This statement is somewhat dubious, however, since
diploid number of chromosomes of this species may not be 25 as they reported
but far more numerous [probably 2n = 78 (male, female): J.C.C. pers. obs.].
Nevertheless, the possibility that XO system also will be found in other opilionids
cannot be excluded. The XO type and its derivatives (XXO, XXXO, etc.) are
ordinary systems in ticks (Oliver 1981) and particularly in Araneae where these
systems are exclusive (Hackman 1948; Suzuki 1954) except for four species of the
salticid genus Pellenes Simon having X1X2X3Y male, X1X1X2X2X3X3 female
system (Maddison 1982) and some populations of huntsman spider, Delena
cancerides Walckenaer having a kind of multiple XY sex-determining mechanism
(Rowell 1985).

ACKNOWLEDGMENTS

N. T. is grateful to the following persons who offered him facilities in this
work: M. Takahashi (Marine Biomedical Institute, Sapporo Medical College), K.
Kito (Sapporo Medical College), T. Okino (Suwa Hydrobiological Station,
Shinshu Univ.), T. A. Uchida (Kyushu Univ.), and C. Shioya, M. T. Chujo
(Hikosan Biological Laboratory, Kyushu Univ.). This study was partly supported
by the Grant-in-Aids (no. 63740434) from the Ministry of Education, Science and
Culture, Japan to N. T. J. C. C. acknowledges the help of L. G. Freihofer, S. R.
Jones, F. Merickel, W. Rogers, F. R. Rose, K. W. Selcer, and S. W. Taber in
collecting materials. The collections of Ms. Freihofer were kindly arranged and
shipped by V. F. Lee of the California Academy of Sciences, San Francisco. J. C.
C. was partly supported by the Departments of Biological Sciences and
Entomology, Texas Tech University, Lubbock.

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Tsurusaki, N. 1985b. Geographic variation of chromosomes and external morphology in the
montanum- subgroup of the Leiobunum curvipalpe- group (Arachnida, Opiliones, Phalangiidae)
with special reference to its presumable process of raciation. Zool. Sci., 2:767-783.

Tsurusaki, N. 1986. Chromosomes of harvestmen (Opiliones, Arachnida): A review of ongoing
research and method of chromosome observation. Seibutsu Kyozai (Kikonai, Hokkaido), No.
21:33-49. (In Japanese)

Tsurusaki, N. and R. G. Holmberg. 1986. Chromosomes of Leiobunum japonicum japonicum and
Leiobunum paessieri (Arachnida, Opiliones). J. Arachnol., 14:123-125.

White, M. J. D. 1973. Animal Cytology and Evolution. 3rd ed. Cambridge University Press,
Cambridge. 961 pp.

White, M. J. D. 1978. Modes of Speciation. W. H. Freeman and Co., San Francisco. 455 pp.

Manuscript received June 1989, revised October 1989.

APPENDIX

Collecting data of the materials. — These are given by the following order: Locality, date collected
(Unless the materials are dissected on the same day or day after, dates of fixation is also given in
parentheses), collector (N. T. = N. Tsurusaki, J. C. C. = J. C. Cokendolpher), number of individuals
(Number in parentheses denotes the number of specimens dissected. This number may be unequal to
the one in Table 1, since there were several slides that contained no countable chromosomal spreads).

1. Caddo agilis. JAPAN: HOKKAIDO; Ebetsu; Nopporo, 18 June 1982 (N. T.), 6 females; same
locality, 21 June 1982 (N. T.), 3 females. 2. Mitopus morio. JAPAN: HOKKAIDO; Is. Rishiri; Mt.
Rishiri, From Oshidomari to Pon-yama, 30-320 m alt., 8 July 1984 (N. T.), 1 male, 5 juveniles (5
juveniles). 3. Homolophus arcticus. JAPAN: HOKKAIDO; Teshio-gun; Toyotomi-cho; Wakasakanai,
9 August 1985 (N. T.), 3 males, 1 female, 16 juveniles (10 juveniles). 4. Homolophus rishiri. JAPAN:
HOKKAIDO; Is. Rishiri; Mt. Rishiri,' Oshidomari route, 670-1000 m alt., 8 August 1985 (N. T.), 2
males, 1 female, 3 juveniles (3 juveniles). 5. Phalangium opilio. U.S.A.: IDAHO; Latan Co.; Moscow,
14 September 1983 (F. W. Merickel), 1 male. 6, Dalquestia formosa. U.S.A.: TEXAS; Kerr Co.; 3.2
km SSE Center Point. 16 September 1983 (W. Rogers), 1 male. 7. Nelima satoi. JAPAN: EHIME
PREF.; Mt. Ishizuchi, From Tsuchigoya to Mt. Iwaguro, 1490-1745 m alt., 5 August 1982 (N. T.), 2
juveniles. FUKUOKA PREF.; Mt. Hiko, 640-700 m alt., 31 July 1982 (N. T.), 2 juveniles. 8. Nelima
similis. JAPAN: NAGANO PREF.: Kami-Ina-gun; Takato, Hokomochi Shrine, 780 m alt., 20 August
1982 (N. T.), 16 males, 7 females, 6 juveniles (4 males). 9. Leiobunum flavum. U.S.A.: TEXAS;
Walker Co.; Sam Houston National Forest, Lake Stubblefield, 29 August 1984 (S. W. Taber), 6 males.
10. Leiobunum towns endi. U.S.A.: TEXAS: Concho Co.; Colorado River crossing at Highway 2134
(31°34’N - 99°41’W), 11 June 1983 (fixed 5 August 1983) (F. L. Rose, L. Robbins and K. W. Selcer),
1 male. 11. Eumesosoma roeweri. TEXAS: Concho Co.; Colorado'' River crossing at Highway 2134
(31°34’N - 99°41’W), 11 June 1983 (F. L. Rose, L. Robbins and K. W. Selcer), 2 males, 2 females;
Kerr Co.; 6.4 km E of Kerrville, 17 May 1984 (S. R. Jones), 3 males, 1 female. 12. Protolophus
tuberculatus. U.S.A.: CALIFORNIA; Marin Co.; San Rafael Ridge at 800 Fawn Drive, San
Anselmo, 15 May 1983 (fixed 22 May 1983) (L. G. Freihofer), 1 male; same locality, 19 March 1984
(fixed 4 April 1984) (L. G. Freihofer), 1 male. 13. Protolophus sp. U.S.A.: CALIFORNIA; Ventura
Co.; Little Sycamore Canyon, ca. 1.6 km N Pacific Coast Highway (35°5’N - 1 18°57’W), 28 June 1985
(fixed 1 July 1985) (J. C. C.), 2 males. 14. Trachyrhinus rectipalpus. U.S.A.: TEXAS; McMullen Co.;
36.8 km S of Tilden, 20 May 1985 (fixed 24 May 1985) (S. W. Taber), 1 male. 15. Melanopa grandis.
JAPAN: NAGANO PREF.; Matsumoto; Lake Misuzu, 980 m alt., 29 June 1984 (fixed 5 July 1984)
(N. T.), 1 juvenile; Mt. Kirigamine, Kowashimizu campground, 1630 m alt., 8 July 1982 (N. T.), 2
juveniles (1 juvenile). TOTTORI PREF.; Mt. Daisen, 760-1100 m alt., 9 August 1982 (N. T.), 14
males, 9 females (2 males). FUKUOKA PREF.; Mt. Hiko, 640-800 m alt., 31 July 1982 (NT.), 7
males, 6 females (3 males). NAGASAKI PREF; Is. Tsushima; Kamitsusima-cho, Hidakatsu, 50-60 m
alt., 26 July 1982 (N. T.), 17 males, 18 females (3 males); Is. Tsushima; Izuhara, Mt. Ariake, 200-530
m alt., 27 July 1982 (N. T.), 9 males, 5 females (3 males). 16. Paraumbogrella pumilio. JAPAN:
HOKKAIDO; Sunagawa, on a levee of River Penke-Utashinai, near the city hall, ca. 25 m alt., 24
September 1986 (N. T.), 1 female; same locality, 1 October 1986 (N. T.), 1 male, 1 female.

Corey, D. T. and I. J. Stout. 1990. Ground surface arachnids in sandhill communities of Florida. J.
Arachnol, 18:167-172.

GROUND SURFACE ARACHNIDS IN SANDHILL
COMMUNITIES OF FLORIDA

David T. Corey1 and I. Jack Stout

Department of Biological Sciences
University of Central Florida
Orlando, Florida 32816 USA

ABSTRACT

Ground surface populations of scorpions, uropygids, pseudoscorpions, solifugids, opilionids, mites,
and ticks were studied for two years using pitfall traps and herp arrays set in twelve sandhill
communities throughout Florida. Three species of pseudoscorpions, 1 species each of uropygids,
solifugids, and scorpions, 5 species of opilionids, and 2 species of ticks were collected. A total of 474
mites were collected. Abundance of pseudoscorpions, uropygids, and acari were significantly
correlated with the total mass of plant litter.

INTRODUCTION

Arachnids associated with the different plant communities of Florida are
poorly known. Recently Corey and Taylor (1987, 1988, 1989) described the
scorpion, pseudoscorpion, opilionid, and spider faunas in pond pine, sand pine
scrub, and flatwoods communities. Pseudoscorpion and spider faunas from a
northwest Florida salt marsh were described by Rey and McCoy (1983).

This paper describes and compares the scorpion, pseudoscorpion, uropygid,
solpugid, opilionid, mite, and tick faunas in twelve sandhill communities
throughout Florida (Laessle 1958; Myers 1985).

STUDY SITES

Twelve sandhill communities were investigated from November 1986 through
December 1988. Each study site was sampled for four days during each season of
the year. Seasons were as follows: winter (December, January, February), spring
(March, April, May), summer (June, July, August), and fall (September, October,
November). Study sites were located throughout Florida (Fig. 1). Site locations
(and abbreviations) were: San Felasco Hammock (SF), Alachua Co.;
Morningside Nature Center (MS), Alachua Co.; Spruce Creek Preserve (SC),
Volusia Co.; Orange City (OC), Volusia Co.; Bok Tower Gardens (BT), Polk Co.;
O’leno State Park (OL), Columbia Co.; Suwannee River State Park (SR),
Suwannee Co.; Wekiwa Springs State Park (WS), Orange Co.; Sandhill Boy
Scout Reservation (BS), Hernando Co.; Janet Butterfield Brooks Preserve (JB),

‘Present address: Department of Zoology, Southern Illinois University, Carbondale, Illinois 62901,

USA.

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Figure 1. — Sandhill study site locations in Florida. See text for abbreviations. Sandhill distributions
(stippled) are based on Davis (1980) and do not reflect minor sites of this community due to the scale
of the illustration.

Hernando Co.; Interlachen (IL), Putnam Co.; Starkey Well Field Area (SW),
Pasco Co.

Sandhills are xeric upland communities. Laessle (1958) and Myers (1985)
provide a general summary of this community type. The tree layer is dominated
by longleaf pine, Pinus palustris , and turkey oak, Quercus laevis. The understory
consists chiefly of wiregrass, Aristida stricta , wild buckwheat, Eriogonum
tomentosum , and saw palmetto, Serenoa repens.

METHODS

Arachnids were collected using 5 pitfall traps and 2 herp arrays. Pitfall traps
were patterned after Muma (1973) and contained a 0.47 1 mixture of ethylene
glycol, water, and 95% ethanol in a ratio 2:1:1. The traps were randomly placed
in each study site during the first collection period. During subsequent collections
the traps were placed in the same location as in the first collecting period.

Two standard herp arrays of drift fences were also used to collect arachnids
(Campbell and Christman 1982). Each array consisted of four sheet metal arms
(7.6 m long) arranged to correspond to the cardinal directions. Two pitfall traps
(21.14 1 plastic buckets) were placed at the ends of each arm, and did not contain
a preservative. Arachnids were removed from pitfalls daily. Two funnel traps
made of fine-mesh wire screen were placed on each side of the sheet metal. The
funnels were located at the midpoint of each arm.

Identification. — All specimens were identified to lowest possible taxon. James
C. Cokendolpher, Texas Tech University, identified the opilionids. William B.
Muchmore, University of Rochester, identified the pseudoscorpions. All other

COREY & STOUT— FLORIDA SANDHILL ARACHNIDS

169

Table 1. — Arachnid fauna collected in sandhill communities in Florida. See text for abbreviations.

ORDER

Collection sites

Species

Totals

SCORPIONIDA

Ceniruroides hentzi (Banks)

PSEUDOSCORPIONES

161

Planctolpium peninsulae

Muchmore

Novohorus obscurus
(Banks)

Paratemnus elongatus

(Banks)

UROPYGI

Mastigoproctus giganteus

(Lucas)

SOLPUGIDA

Ammotrechella stimpsoni

(Putnam)

OPILIONES

Leiobunum aurugineum

Crosby & Bishop

206

L. bimaculatum Banks

Eumesosoma nigrum (Say)

Hadrobunus sp.

124

Vonones ornata Say
ACARINA

Mites

166

474

Ticks

Amblyomma americanum (L.)

Dermacentor variabilis Say

TOTALS

130

206

122

103

132

114

1054

identifications were made by the senior author. Voucher specimens have been
deposited at Florida State Collection of Arthropods, Division of Plant Industries,
Gainesville, Florida.

Ground-level vegetation was sampled to determine if these microhabitat
features were correlated with the abundance of arachnids. Twenty points were
selected at random, and woody plants less than 2.54 cm in diameter at 1.37 m
above the ground were counted in plots (3x2 m). Plot sides were used as line
transects (5 m) to measure the canopy interception of grasses and herbs. Lastly,
10 plots (0.1 m2 each) were randomly positioned and leaf litter collected, oven-
dried, and the mass determined to the nearest gram. All measurements were taken
during the second year of study. Pearson correlation coefficient was used to test
the relationship between group abundance and ground level habitat features of
the sandhill study sites (SAS Institute 1985).

RESULTS AND DISCUSSION

A total of 1054 arachnids belonging to 6 orders were collected. Species
composition, total number of individuals trapped, and percentage collected with
each method in the twelve study sites are listed in Tables 1 and 2. Comparison of
seasonal and yearly abundance are in Table 3.

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Table 2. — Percentage of arachnids collected by funnels (F), buckets (B), and pitfall traps (P).

ORDER

Species

Methods

SCORPIONIDA

Centruroides hentzi (Banks)

5.0

95.0

0.0

PSEUDOSCORPIONES

Planctolpium peninsulae Muchmore

0.0

31.3

68.7

Novohorus ohscurus (Banks)

0.0

100.0

0.0

Paratemnus elongatus (Banks)

0.0

33.3

66.7

UROPYGI

Mastigoproctus giganteus (Lucas)

0.0

100.0

0.0

SOLPUGIDA

Ammotrechella stimpsoni (Putnam)

0.0

75.0

25.0

OPILIONES

Leiobunum aurugineum Crosby & Bishop

55.0

39.3

5.7

L. bimaculatum Banks

53.3

46.7

0.0

Eumesosoma nigrum (Say)

0.0

50.0

Hadrobunus sp.

19.4

39.3

5.7

Vonones ornata Say

8.3

25.0

66.7

ACARI

Mites

0.4

12.0

87.6

Ticks

Amblyomma americanum (L.)

0.0

100.0

Dermacentor variabilis Say

0.0

100.0

TOTALS

One-hundred and sixty-one scorpions of a single species, Centruroides hentzi
(Banks), were collected. Correlation (r) of scorpion abundance with ground-level
habitat features is given in Table 4. No significant correlations were found, but
scorpions were less abundant where shrubs were more common and plant litter
accumulation was greater. Centruroides hentzi is commonly found under stones,
logs, litter, and also under bark of dead standing trees (Muma 1967).

Males represented 67.7% of the total number of scorpions collected, while
females represented 19.3% of the total population. Twenty-one juveniles were
collected. All juveniles were collected in March, May, November, Tnd February.
Corey and Taylor (1987) collected 86% of their C. hentzi population from July
through September, with all juveniles being collected in September. They found
the greatest number of individuals in sand pine scrub, an upland xeric community
with a well-developed shrub layer (Laessle 1958; Myers 1985).

Table 3. — Percentage of arachnids collected by season and year in the twelve sandhill study sites.

1st Year

2nd Year

Order

Fall

Winter Spring Summer

Total

Fall

Winter Spring Summer

Total

Scorpionida

9.9

3.7

13.7

7.5

34.8

19.3

5.6

24.2

16.1

65.2

Pseudoscorpiones

0.0

13.6

9.1

4.6

27.3

0.0

50.0

22.7

72.7

Uropygi

18.2

0.0

18.2

54.5

0.0

27.3

81.8

Solpugida

20.0

0.0

20.0

0.0

60.0

0.0

80.0

Opiliones

Acari

13.9

20.1

15.5

12.3

61.8

10.2

15.0

3.2

9.8

38.2

mites

36.2

5.1

23.0

4.2

68.5

1.3

5.9

12.9

11.4

31.5

ticks

10.0

60.0

0.0

80.0

0.0

20.0

0.0

20.0

COREY & STOUT— FLORIDA SANDHILL ARACHNIDS

171

Table 4.— Correlation (r) of arachnid abundance with ground-level habitat features of sandhill study
sites in Florida. *= r value significant at P<0.05.

Correlation of arachnid abundance with habitat features

Order

Shrub density
(no./m2)

Grass-herb
ground cover
(cm)

Mass of
plant litter
(g)

Scorpionida

-0.516

0.237

-0.349

Pseudoscorpiones

-0.158

-0.216

0.601*

Uropygi

-0.056

-0.022

0.590*

Solpugida

-0.508

0.510

-0.330

Opiliones

-0.364

-0.209

0.094

Acari

-0.076

-0.354

0.620*

Two of the three species of pseudoscorpions found in sandhills, Planctolpium
peninsulae Muchmore and Novohorus obscurus (Banks), were collected by Corey
and Taylor (1987). They collected P. peninsulae from a sand pine scrub
community and N. obscurus from pond pine, sand pine scrub, and pine flatwoods
communities.

Pseudoscorpions spend most of their time in small crevices (Weygoldt 1969).
Such microhabitat features on our study sites were associated with the bark of
standing or fallen tree trunks and litter. Our sampling devices captured occasional
individuals moving on the ground surface and probably underestimated the
abundance of pseudoscorpions. A significant correlation (r = 0.601, P <0.05) was
found between pseudoscorpion abundance and mass of plant litter (Table 4).

Eleven Uropygi from a single species, Mastigoproctus giganteus (Lucas), were
collected. These animals are often found under rotten logs and other debris on
the surface of the ground (Muma 1967).

Five individuals of the solpugid Ammotrechella stimpsoni (Putnam) were
collected. This is the only solpugid that occurs in peninsular Florida (Muma
1967).

A total of 371 opilionids representing 5 species and 2 families were collected.
Vonones ornata Say was the most common opilionid collected by Corey and
Taylor (1987), and was found in sand pine scrub, pond pine, and pine flatwoods
communities.

Opilionids were not found to be correlated with (P > 0.05) shrub density,
ground cover, or plant litter (Table 4).

Two individuals of Eumesosoma nigrum (Say) were collected. This species is
found throughout the year in moist places under debris (Cokendolpher 1980).

Jennings, Houseweart, and Cokendolpher (1984) used pitfall traps to sample
the epigeal phalangid fauna in strip clearcut and dense spruce-fir forest of Maine.
They collected a total of 8 species, with 1 or 2 species being more abundant than
the others in each habitat. Carter and Brown (1973) reported six species from
pitfall traps in New Brunswick.

Tick and mites (Acari) represented 45.9% of the total arachnid population and
were significantly correlated (P < 0.05) with the mass of plant litter (Table 4).
Mites comprised 97.9% of the Acari. Two species of ticks were collected:
Amblyomma americanum (Linnaeus) and Dermacentor variabilis Say.

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THE JOURNAL OF ARACHNOLOGY

ACKNOWLEDGMENTS

We thank J. C. Cokendolpher and W. B. Muchmore for identifying specimens.
V. F. Lee and W. A. Shear made critical comments on an earlier draft of the
manuscript. The following individuals or agencies allowed access to their property
to conduct the research: Ellis Collins (Interlachen), Fred Hunt (Orange City), Bok
Tower Gardens, Sandhill Boy Scout Reservation, Morningside Nature Center,
Nature Conservancy (Spruce Creek Preserve and Janet Butterfield Brooks
Preserve), South West Florida Water Management District (Starkey Well Field
Area), and the Division of Recreation and Parks of the Florida Department of
Natural Resources (San Felasco Hammock, Wekiwa Springs State Park, O’leno
State Park, and Suwannee River State Park). This work was supported by
Nongame Wildlife Program Contract No. RFP-86-003 from the Florida Game
and Fresh Water Fish Commission to I. J. Stout and the Exline-Frizzell Fund for
Arachnological Research, Grant No. 33 from the California Academy of Sciences
to D. T. Corey.

LITERATURE CITED

Campbell, H. W. and S. P. Christman. 1982. Field techniques for herpetofaunal community analysis.
Pp. 193-200, In Herpetological Communities. (N. J. Scott, Jr., ed.). U.S. Fish and Wildlife Service,
Wildlife Research Report 13.

Carter, N. E. and N. R. Brown. 1973. Seasonal abundance of certain soil arthropods in a fenitrothion-
treated red spruce stand. Can. Entomol., 105:1065-1073.

Cokendolpher, J. C. 1980. Replacement name for Mesosoma Weed, 1982, with a revision of the genus
(Opiliones, Phalangiidae, Leiobuninae). Occ. Pap. Mus. Texas Tech Univ., 66:1-19.

Corey, D. T. and W. K. Taylor. 1987. Scorpion, pseudoscorpion, and opilionid faunas in three central
Florida plant communities. Florida Scient., 50:162-167.

Corey, D. T. and W. K. Taylor. 1988. Ground surface spiders in three central Florida plant
communities. J. Arachnol., 16:213-221.

Corey, D. T. and W. K. Taylor. 1989. Foilage-dwelling spiders in three central Florida plant
communities. J. Arachnol., 17:97-106.

Davis, J. H. 1980. General map of natural vegetation of Florida. Agr. Exp. Sta., Inst. Food and Agr.
Sci. Circular S-178. University of Florida, Gainesville. 1 p.

Jennings, D. T., M. W. Houseweart and J. C. Cokendolpher. 1984. Phalangids (Arachnida: Opiliones)
associated with strip clearcut and dense spruce-fir forest of Maine. Environ. Entomol., 13:1306-
1311.

Laessle, A. M. 1958. The origin and successional relationship of sandhill vegetation and sand-pine
scrub. Ecol. Monogr., 28:361-387.

Muma, M. H. 1967. Scorpions, whipscorpions, and wind scorpions of Florida. Arthropods Florida
Neighboring Land Areas, 4:1-28.

Muma, M. H. 1973. Comparison of ground surface spiders in four central Florida ecosystems. Florida
Entomol., 56:173-196.

Myers, R. L. 1985. Fire and the dynamics relationship between Florida sandhill and sand pine scrub
vegetation. Bull. Torrey Bot. Club, 112:241-252.

Rey, J. R. and E. D. McCoy. 1983. Terrestrial arthropods of northwest Florida salt marshes: Araneae
and Pseudoscorpiones (Arachnida). Florida Entomol., 66:497-503.

SAS Institute. 1985. User’s Guide: Statistics, Version 5 edition. SAS Institute, Cary, North Carolina.

Weygoldt, P. 1969. The Biology of Pseudoscorpions. Harvard University Press, Cambridge,
Massachusetts.

Manuscript received October 1989, revised December, 1989.

Jennings, D. T., W. M. Vander Haegen and A. M. Narahara. 1990. A sampling of forest-floor spiders
(Araneae) by expellant. Moosehorn National Wildlife Refuge, Maine. J. Arachnol, 18:173-179.

A SAMPLING OF FOREST FLOOR SPIDERS
(ARANEAE) BY EXPELLANT,
MOOSEHORN NATIONAL WILDLIFE REFUGE, MAINE

Daniel T. Jennings1

Northeastern Forest Experiment Station
USDA Building
University of Maine
Orono, Maine 04469 USA

W. Matthew Vander Haegen and Annie M. Narahara

Maine Cooperative Fish and Wildlife Research Unit
240 Nutting Hall
University of Maine
Orono, Maine 04469 USA

ABSTRACT

Spiders of 14 families, 34 genera, and at least 36 species were collected by formalin extraction from
sub-litter habitats of the forest floor, Moosehorn National Wildlife Refuge, Washington County,
Maine, in 1987. Species per family ranged from 1 to 7; the Erigonidae had the richest representation
with 19.4% of all species. Most species (64.0%) were represented by sexually mature spiders; the ratio
of female to male spiders was 3.2:1. Species of web-spinning spiders outnumbered species of hunting
spiders 2 to 1. Numbers of spiders/ 0.25 m2 circular plot ranged from 1 to 4; mean overall density of
sub-litter spiders was 1.12 + 0.17 SE, where N = 36 plots. Most (67.3%) of the spiders were
associated with only one forest-stand type, possibly indicating species-habitat specificity.

INTRODUCTION

Spiders are increasingly recognized as important components of forest
ecosystems (e.g., Moulder and Reichle 1972); however, relatively few studies have
addressed the forest-floor araneofauna of particular forest-stand types. For
northeastern forests of the United States and Canada, spruce-fir (Picea- Abies)
stands have received the most attention (Freitag et al. 1969; Rudolf 1970; Carter
and Brown 1973; Varty and Carter 1974; Jennings et al. 1988; Hilburn and
Jennings 1988). Northern hardwood stands and mixed hardwood-softwood stands
have received much less attention (Cutler et al. 1975), particularly those in Maine
(Procter 1946). Most araneological studies of hardwood types concern forest-litter
spiders of southern and midwestern deciduous forests (Bultman and Uetz 1984;
Coyle 1981; Gasdorf and Goodnight 1963; Uetz 1979).

‘Present address: Northeastern Forest Experiment Station, 180 Canfield Street, P. O. Box 4360,
Morgantown, West Virginia 26505.

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THE JOURNAL OF ARACHNOLOGY

As part of an investigation on the bioenergetics of the American woodcock,
Scolopax minor , spiders were collected by a limited sampling technique from
numerous forest-floor habitats of the Moosehorn National Wildlife Refuge in
eastern Maine. Because detailed information was taken on tree-species
composition and forest-stand type, these collections provide descriptive, habitat-
associational information for the collected spider species.

METHODS

Spiders were collected from the soil surface following litter removal and
formalin extraction on 36 circular 0.25-rn2 plots established temporarily at several
locations on the Moosehorn National Wildlife Refuge, Calais and Baring Minor
Civil Divisions, Washington County, Maine. The collections were made from 24
April to 16 June 1987, with plot-sampling dates distributed unevenly among
months; April (TV = 3 dates), May ( TV — 14), and June ( TV = 6). Plots were
located at sites used by radio-marked woodcock and were sampled only once.
Because of differential selection of forest stands by woodcock, the 36 sampling
plots were distributed unevenly among forest-stand types, predominantly
deciduous trees ( N = 27 plots), coniferous trees (TV = 8), and mixed coniferous-
deciduous trees ( TV = 1). Forest-stand types were determined by a modified
version (G. F. Sepik, Moosehorn NWR, unpubl.) of the Society of American
Foresters (SAF) classification system (Eyre 1980). Each stand type was
characterized by one or two predominant tree species. Deciduous tree species
were: speckled alder, Alnus rug os a; bigtooth aspen, Populus grandidentata;
quaking aspen, P. tremuloides ; red maple, Acer rubrum ; gray birch, Betula
populifolia\ and paper birch, B. papyrifera. Coniferous tree species were: balsam
fir, Abies balsamea ; spruces, Picea spp.; and eastern white pine, Pinus strobus.
Common and species names of trees follow Fittle (1979).

At each site, a 0.25-m2 ring (PVC pipe) was placed on the ground and all leaf
litter removed down to the humus-mineral soil layer (Fig. 1). Spiders were not
collected from the loose leaf litter; however, some litter-inhabiting species
probably descended to the soil as the litter was removed. After litter removal, a
0.2% formalin solution was poured over the soil to extract spiders and
earthworms (Reynolds et al. 1977). All spiders captured within 10 minutes
following application of the expellant were placed in 75-80% ethanol.

For the most part, only sexually mature spiders were identified to species.
Juvenile and penultimate stages were identified to family or generic level.
Representative specimens of most spider species found will be deposited in the
arachnid collections of the U.S. National Museum of Natural History,
Washington, DC.

RESUFTS

JENNINGS ET AL.— FOREST-FLOOR SPIDERS

175

Figure 1. — Ring of PVC pipe used to delineate 0.25-m2 plots. Spiders were collected from the sub-
litter layer after removal of leaf-litter.

Species of web-spinning spiders (66.7%) outnumbered species of hunting spiders

(33.3%) 2 to h

Eighty-one spiders were collected from the 36 circular 0.25-m2 plots.
Individuals were distributed unevenly among life stages; juveniles and penultimate
stages comprised 58% of all specimens, while sexually mature males and females
made up the remaining 42%. Overall, more females (X = 26) than males (2 = 8)
were collected.

Because of the limited sampling method used, the number of spiders per plot
was very low, ranging from 1 to 4. The mean overall density of spiders collected
from sub-litter habitats was 1.12 + 0.17 SE, where TV = 36 0.25-m2 circular plots.

The frequency distribution of forest-stand types among spider taxa ranged from
1 to 4 (Table 1). Most (67.3%) of the spiders were associated with only one forest-
stand type; few (32.7%) were found in two or more stand types. As expected,
spider species and individuals paralleled the apportionment of plots among forest-
stand types (Table 2). Interestingly, nearly all (87.5%) of the hunting spiders were
collected from stands with predominantly deciduous trees; few were collected
from stands with coniferous trees.

DISCUSSION

Most of the species of spiders collected during this study are typical ground-
inhabiting species often associated with forest leaf litter. Many have been taken
by pitfall traps in spruce-fir forests of central and west-central Maine (Jennings et
al. 1988; Hilburn and Jennings 1988); others have been collected from under
stones and among dead leaves and by sifting spring-flood debris in Connecticut
(Kaston 1981). The species we collected that appear unusual for forest-floor

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Table 1. — Species and numbers of spiders collected from 36 circular 0.25-m2 plots, sub-litter
habitats of the forest floor, Moosehorn National Wildlife Refuge, Maine, 1987.

FAMILY

Genus species

Males

Number

Females

juv.

Forest-stand type

WEB SPINNERS

AGELENIDAE

(0)

(3)

(5)

Agelenopsis sp.

Alder

Cicurina brevis (Emerton)

Aspen-Maple; W. Pine-

Aspen; W. Pine

Cicurina sp.

Aspen; Maple-P. Birch;

Maple-G. Birch

Wadotes sp.

Maple

HAHNIIDAE

(0)

(1)

Antistea brunnea (Emerton)

Alder-Aspen

Undet. sp.

W. Pine

AMAUROBIIDAE

(1)

(4)

Amaurobius borealis Emerton

Alder; Aspen; Maple

Amaurobius sp.

Alder

Callobius bennetti (Blackwall)

Aspen-Maple

Undet. sp.

Alder; Alder-Aspen

DICTYNIDAE

(0)

(1)

Dictyna minuta Emerton

Alder

Dictyna sp.

Balsam fir

THERIDIIDAE

(1)

(4)

(6)

Euryopis argentea Emerton

Spruce-Fir

Robertus riparius (Keyserling)

Alder; W. Pine

Theridion aurantium Emerton

Spruce-Fir

Theridion sexpunctatum Emerton

Balsam fir

Theridion sp.

Alder; Aspen

Undet. sp.

Alder; Maple; Balsam

fir

LINYPHIIDAE

(0)

(2)

Lepthyphantes zebra (Emerton)

Aspen; W. Pine-Aspen

Prolinyphia marginata (C. L. Koch)

Spruce-Fir

Undet. sp.

Aspen-Maple

ERIGONIDAE

(3)

(5)

(7)

Ceraticelus fissiceps (O.P.-Cambridge)

Maple-G. Birch

Diplocephalus cuneatus Emerton

Aspen

Hypselistes florens (O.P.-Cambridge)

Aspen

Maso sundevallii (Westring)

Alder; Maple-G. Birch

Tunagyna debilis (Banks)

Aspen

Walckenaeria auranticeps (Emerton)

G. Birch

Walckenaeria directa (O.P.-Cambridge)

Maple-Aspen

Undet. sp.

Aspen; Maple-Aspen; W.

Pine; Balsam fir

ARANEIDAE

(0)

(1)

(4)

Araneus sp.

Spruce-Fir

M angora placida (Hentz)

Balsam fir

Mangora sp.

Aspen

Neoscona sp.

Aspen; Maple-Aspen

TETRAGNATHIDAE

(0)

(1)

Tetragnatha sp.

Aspen

JENNINGS ET AL,— FOREST FLOOR SPIDERS 177

HUNTERS

LYCOSIDAE

(0)

(6)

Pardos a sp.

Aspen

Pirata sp.

Alder-Aspen; Maple-

Aspen

Trochosa sp.

Aspen; W. Pine

GNAPHOSIDAE

(1)

(0)

(1)

Callilepis sp.

Aspen-Maple

Zelotes fratris Chamberlin

Aspen-Maple

CLUBIONIDAE

(0)

(4)

(2)

Agroeca ornata Banks

Aspen

Clubiona sp.

Aspen

Phrurotimpus alarms (Hentz)

Aspen; Aspen-Maple

Phmrotimpus sp.

Aspen

THOMISIDAE

(1)

(5)

Ozyptila sp.

W. Pine

Xysticus elegans Keyserling

Aspen; Aspen-Maple

Xysticus sp.

Maple-Aspen; G. Birch;

Maple-G. Birch;
Balsam fir

SALTICIDAE

(1)

(0)

(2)

Habrocestum sp.

Aspen

Metaphidippus flaviceps Kaston

Aspen

Metaphidippus sp.

Aspen

habitats include Araneus sp., Mangora placida (Hentz), Neoscona sp., Hypselistes
florens (O.R-Cambridge), Prolinyphia marginata (C. L. Koch), Tetragnatha sp.,
and Metaphidippus flaviceps Kaston. Because these species generally are
associated with herb-shrub-tree strata, we suspect that individuals descended from
upper levels to the forest floor.

Seven of the species of spiders collected by formalin extraction from forest-
floor habitats of the Moosehorn National Wildlife Refuge have not been captured
by extensive pitfall trapping in coniferous forests of Maine (Jennings et al. 1988;
Hilburn and Jennings 1988). These include species represented by sexually mature

spiders — Dictyna minuta Emerton, Walckenaeria auranticeps (Emerton), Euryopis

Table 2. — Distribution of forest-floor plots and collected spiders among three groups of forest-stand
types, Moosehorn National Wildlife Refuge, 1987. *Groupings based on predominant trees; see text
for tree species, t Mixed coniferous-deciduous trees. ft Conservative estimate; excludes undetermined
species. Some species were found in more than one forest-stand type.

Forest-stand type*

Deciduous Coniferous Mixedf

Parameter

(%)

Plots

(75.0)

(22.2)

(2.8)

Speciestt

web spinners

(64.5)

(29.0)

(6.4)

hunters

(78.6)

(21.4)

(0.0)

Individuals

web spinners

(70.2)

(26.3)

(3.5)

hunters

(87.5)

(12.5)

(0.0)

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THE JOURNAL OF ARACHNOLOGY

argentea Emerton, and Phrurotimpus alarms (Hentz) — and species represented
only by juveniles — Callilepis sp., Habrocestum sp., and Ozyptila sp. Little is
known about their specific micro-habitat requirements; our data on forest-stand
associations broaden the range of known habitats for these species.

No doubt, our sampling method (i.e., removal of litter without sorting for
spiders) greatly contributed to the relatively low densities of spiders observed in
sub-litter habitats of Maine. Hand sorting the litter, or extraction of leaf-litter
spiders by Berlese or Tullgren funnel (Southwood 1978) should substantially add
species and individuals to the list of spiders from forest-floor habitats.

Collection of spiders by expellant yielded a greater proportion (3.2:1) of
females to males. Pitfall traps, on the other hand, are selectively biased toward
capture of male spiders. Male spiders generally are more mobile and may move
considerable distances in search of female spiders; hence, the sexes are seldom
equally represented in pitfall-trap catches (Hallander 1967; Muma 1975).

Our study suggests that forest-floor spiders are not confined to the leaf-litter
layer; we collected spiders from the sub-litter layer. After treatment with
formalin, some spiders emerged from cracks and crevices in the soil. However,
some of the spiders in our samples may have descended from upper layers,
including leaf-litter and herb-shrub-tree strata.

Results of this study indicate that the araneofauna associated with forest-floor
habitats of the Moosehorn National Wildlife Refuge is: (1) diverse, (2) composed
of species and individuals that represent at least two spider-foraging strategies,
and (3) possibly habitat specific, with few species shared in common among
forest-stand types. Additional studies are needed to better define the araneofauna
of any one forest-stand type. Studies also are needed to compare sampling
methodologies (e.g., expellant vs pitfall-traps) at the same time, place, and
stratum. On the basis of our study and previous studies (Bultman and Uetz 1984;
Carter and Brown 1973; Uetz 1975, 1979), we predict that each forest-stand type
will be composed of spider-species assemblages that are characteristic and
descriptive for that type.

ACKNOWLEDGMENTS

We are grateful to D. Mullen and G. F. Sepik, both of the Moosehorn
National Wildlife Refuge, Calais, Maine, for logistical support. Constructive
manuscript reviews were provided by Drs. B. M. Blum, M. E. Dix, D. R.
Folkerts, N. V. Horner, W. B. Krohn and G. W. Uetz. We thank J. J. Melvin for
word processing. Portions of this research were funded by the U.S. Department
of the Interior, Fish and Wildlife Service, and the College of Forest Resources,
University of Maine, through cooperative research agreement 9155F-8.

LITERATURE CITED

Bultman, T. L. and G. W. Uetz. 1984. Effect of structure and nutritional quality of litter on
abundances of litter-dwelling arthropods. Amer. Midi Nat., 93:239-244.

Carter, N. E. and N. R. Brown. 1973. Seasonal abundance of certain soil arthropods in a fenitrothion-
treated red spruce stand. Canadian Entomol., 105:1065-1073.

Coyle, F. A. 1981. Effects of clearcutting on the spider community of a southern Appalachian forest.
J. Arachnol., 9:285-298.

JENNINGS ET AL. — FOREST-FLOOR SPIDERS

179

Cutler, B., L. H. Grim and H. M. Kulman. 1975. A study in the summer phenology of dionychious
spiders from northern Minnesota forests. Great Lakes Entomol., 8:99-104.

Eyre, F. H., ed. 1980. Forest Cover Types of the United States and Canada. Soc. Amer. Foresters,
Washington, DC. 148 pp.

Freitag, R., G. W. Ozburn and R. E. Leech. 1969. The effects of sumithion and phosphamidon on
populations of five carabid beetles and the spider Trochosa terricola in northwestern Ontario and
including a list of collected species of carabid beetles and spiders. Canadian Entomol, 101:1328-
1333.

Gasdorf, E. C. and C. J. Goodnight. 1963. Studies on the ecology of soil arachnids. Ecology, 44:261-
268.

Hallander, H. 1967. Range movement of the wolf spiders Pardosa chelata (O. F. Muller) and P

pullata (Clerck). Oikos, 18:360-369.

Hilburn, D. J. and D. T. Jennings. 1988. Terricolous spiders (Araneae) of insecticide-treated spruce-fir
forests in west-central Maine. Great Lakes Entomol, 21:105-1 14.

Jennings, D. T., M. W. Houseweart, C. D. Dondale and J. H. Redner. 1988. Spiders (Araneae)
associated with strip-clearcut and dense spruce-fir forests of Maine. J. Arachnol, 16:55-70.

Kaston, B. J. 1981. Spiders of Connecticut. Bull. Connecticut State Geol. Nat. Hist. Surv., 70. 1020

pp.

Little, E. L., Jr. 1979. Checklist of United States trees (native and naturalized). U.S. Dept. Agric.,
Agric. Handb., 541. 375 pp.

Moulder, B. C. and D. E. Reichle. 1972. Significance of spider predation in the energy dynamics of
forest-floor arthropod communities. Ecol. Monogr., 42:473-498.

Muma, M. H. 1975. Long term can trapping for population analyses of ground-surface, arid-land
arachnids. Florida Entomol, 58:257-270.

Procter, W. 1946. Biological survey of the Mount Desert region incorporated. Part VII. The Insect
Fauna. The Wistar Institute of Anatomy and Biology. Philadelphia, Pennsylvania. 566 pp.

Reynolds, J. W., W. B. Krohn and G. A. Jordan. 1977. Earthworm populations as related to
woodcock habitat usage in central Maine. Proceed. Woodcock Symposium 6:135-146. Fredericton,

New Brunswick. Oct. 4-6, 1977.

Rudolf, P. J. 1970. Spiders of the forest floor in two stands of red spruce ( Picea rubens Sarg.) in the
University of New Brunswick Forest. M. Sc. F. Thesis, Univ. New Brunswick, Fredericton, New
Brunswick. 60 pp.

Southwood, T. R. E. 1978. Ecological Methods, with a Particular Reference to the Study of Insect
Populations. Chapman and Hall, London. 524 pp.

Uetz, G. W. 1975. Temporal and spatial variation in species diversity of wandering spiders in
deciduous forest litter. Environ. Entomol, 4:719-724.

Uetz, G. W. 1979. The influence of variation in litter habitats on spider communities. Oecologia,
40:29-42.

Varty, I. W. and N. E. Carter. 1974. Inventory of litter arthropods and airborne insects in fir-spruce
stands treated with insecticides. Canadian For. Serv., Maritimes For. Res. Cent. Inf. Rep., M-X-
48. 32 pp.

Manuscript received May 1989, revised December 1989.

■

Jennings, D. T., J. B. Diamond and B. A. Watt. 1990. Population densities of spiders (Araneae) and
spruce budworms (Lepidoptera, Tortricidae) on foliage of balsam fir and red spruce in east-central
Maine. J. ArachnoL, 18:181-193.

POPULATION DENSITIES OF SPIDERS (ARANEAE)

AND SPRUCE BUDWORMS (LEPIDOPTERA, TORTRICIDAE)
ON FOLIAGE OF BALSAM FIR AND RED SPRUCE
IN EAST-CENTRAL MAINE

Daniel T. Jennings

Northeastern Forest Experiment Station
USDA Building, University of Maine
Orono, Maine 04469 USA

and

John R. Dimond and Bruce A. Watt

Department of Entomology
University of Maine
Orono, Maine 04469 USA

ABSTRACT

Spiders of 10 families, 17 genera, and at least 22 species were collected from crown foliage samples
of Abies baisamea (L.) Mill, and Picea rubens Sarg. in east-central Maine. Species of web spinners
were more prevalent (68.2% of total species) among branch samples (N = 613 branches) than species
of hunters (31.8%). Mean species per site (N = 8 sites) was 7.6 ± 1.2. Numbers, life stages, and sex
ratios of spiders differed between tree species; sex ratios were biased (G-test, P < 0.001) in favor of
females. Spider densities per m2 of foliage area generally were greater (P < 0.05) on red spruce (X =
12.0 ± 1.3) than on balsam, fir (X = 7.2 + 0.9), but sampling intensity was important. For intensely
sampled sites, overall mean densities of spruce budworms/ m2 of foliage were not significantly different
(P > 0.05) between tree species. Spearman’s rank correlation coefficients indicated that spider-
bud worm densities covaried weakly among study sites for each tree species; balsam fir ((rho) = 0.17,
N = 343), red spruce ((rho) = 0.15, N = 270). Enhancement of spider populations through
silvicultural treatments designed to favor spruces is proposed.

INTRODUCTION

The spruce bud worm, Choristoneura fumiferana (Clem.), is the most widely
distributed and destructive defoliator of spruce-fir ( Picea-Abies ) forests in North
America (Talerico 1984). Conservation and enhancement of natural enemies of
the spruce budworm are desirable goals of integrated pest management (IPM)
systems directed against this forest pest (Simmons et ah 1984). Because spiders
are predators of all life stages of the spruce budworm (Jennings and Crawford
1985), they are receiving increased attention from investigators (Renault and
Miller 1972; Jennings and Collins 1987; Jennings and Houseweart 1989). Part of
this interest stems from the potential to enhance or increase spider populations
through habitat manipulations (Riechert and Lockley 1984; Provencher and
Vickery 1988; Jennings et ah 1988; Riechert and Bishop 1990).

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Spiders respond to structural features within habitats (Greenquist and Rovner
1976), and vegetation structure, complexity, and diversity are important
parameters that influence spider numbers and richness (Lubin 1978; Greenstone
1984; Riechert and Gillespie 1986; Young 1989). Because of these attributes, it
might be possible to enhance or increase spider populations in northeastern
spruce-fir forests by selecting or favoring tree species that harbor abundant
spiders. For example, Stratton et al. (1979) found that white spruce, Picea glauca ,
had more spiders (both numbers of individuals and numbers of species) than red
pine, Pinus resinosa , or northern white-cedar, Thuja occidental is, in Minnesota.
Likewise, Jennings and Dimond (1988) found that spider densities generally were
greater on spruces (white spruce and red spruce, Picea ruhens) than on balsam
fir, Abies balsamea, in Maine. By increasing the percentage tree-species
composition of spruces in forest stands, it may be possible to increase population
densities of arboreal spiders in these stands. However, we must first determine the
species of spiders associated with northeastern conifers, assess their respective
population densities, and determine their population enhancement potential.

In 1987, we collected additional data on the population densities of spiders and
spruce budworms associated with tree-crown foliage of red spruce and balsam fir
in east-central Maine. These data complement and support our earlier findings in
east-central Maine (Jennings and Dimond 1988); they also provide historical
records (1985-1987) of spider-budworm densities during the decline phase of a
spruce budworm epidemic. In this paper we describe the arboreal spider fauna
associated with balsam fir and red spruce, compare spider and spruce budworm
population densities among study sites and between host-tree species, explore
spider-budworm density relationships, and discuss possible pest management
implications of our findings in east-central Maine.

METHODS

Study areas. — Eight forest stands in east-central Maine (Fig. 1) were sampled
in 1987. Three of these stands were previously sampled in 1986 (Jennings and
Dimond 1988). All sites were in open, spruce-fir stands that had declining
populations of the spruce budworm. Study-site abbreviations and their locations
by town, township, and county were:

(MA) — Myra I, T32 MD, Hancock County
(MY) — Myra II, T32 MD, Hancock County
(DL) — Deer Lake, T34 MD, south, Hancock County
(MR) — Machias River, T30 MD, Washington County
(HM) — Hermon Mtn., T31 MD, Washington County
(GP) — Georges Pond, Franklin, Hancock County
(SH) — Sugar Hill, Eastbrook, Hancock County
(NL) — Narraguagus Lake, T9 SD, Hancock County

At each location, trees along old logging roads and forest trails were selected
for sampling based on tree dominance and accessibility. This resulted in variable-
plot sizes with linear transects ranging from 0.5 to 1 km. At most sites, 10
dominant/ codominant trees of each species (balsam fir, red spruce) were selected,
flagged, and numbered for consecutive sampling on a weekly basis.

JENNINGS ET AL. — SPIDER-BUD WORM DENSITIES

183

Figure L — Study-site locations In east-central
Maine for sampling spider and spruce budworm
densities, 1987. (See text for detailed descriptions
of locations).

Branch samples, — We used a long, sectional pole pruner to cut one 45-cm
branch from the upper crown half of each selected tree. The pole pruner was
equipped with a cloth-basket attachment for catching any spiders and budworms
dislodged when the branch was cut (Jennings and Collins 1987). Once lowered to
the ground, severed branches and dislodged arthropods were removed from the
basket and placed individually in labeled plastic bags for transport to the
laboratory.

In the laboratory, technicians clipped the sample branches into small lengths
(8-10 cm) and closely searched all foliage for spiders and spruce budworms. All
collected spiders were stored in 2-dram vials containing 75% ethanol. Labels with
study-site location, sample date, and branch-tree species were placed inside each
vial

For most study sites, selected trees were sampled at about weekly intervals
beginning 27 May and ending 1 July 1987. However, balsam fir and red spruce
were sampled only once (11 June 1987) at Georges Pond (GP), Narraguagus Lake
(NL), and Sugar Hill (SH).

Spider identifications. — Sexually mature spiders were Identified to species;
juveniles, Including penultimate stages, were identified to genus. However,
juveniles of some philodromid spiders were identified to species (i.e., Philodromus
placidus Banks) or species group ( aureolas , mfus) based on color patterns of legs,
carapace, and abdomen (Dondale and Redner 1978). Representative specimens of
all identified species will be deposited in the arachnid collection, U. S. National
Museum of Natural History, Washington, DC.

Data analyses. — Branch surface areas of balsam fir and red spruce were
calculated by the formula; A = {LX W)j 2, where L is the foliated branch length
and W is the maximum foliated width (Sanders 1980). Population densities of

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both spiders and spruce bud worms were expressed as numbers of individuals/ m2
of branch surface area. Because sampling intensities varied among study sites, we
grouped the samples into high- and low-intensity sites. The Kruskal-Wallis Test
(SAS Institute 1985) was used to compare spider-budworm densities among study
sites and between tree species at P = 0.05. We used Spearman’s rank correlation
coefficient (rho) to test for independence between spider and budworm densities.
The (/-statistic (Sokal and Rohlf 1981) was used to compare sex ratios of
collected spiders, where the expected proportions were 0.50 males and 0.50
females. The (/-statistic was also used to compare species composition of spiders
by foraging strategy, where the expected proportions were: balsam fir — 0.57 web
spinners, 0.43 hunters; red spruce — 0.64 web spinners, 0.36 hunters (Jennings and
Dimond 1988).

RESULTS

Forest stands. — The study sites sampled in 1987 were similar to those
previously investigated (Jennings and Dimond 1988). Balsam fir and red spruce
were the principal softwood components, with occasional eastern white pine,
Pinus strobus, eastern hemlock, Tsuga canadensis , and northern white-cedar.
Hardwood components were maples ( Acer spp.) and birches {Be tula spp.). Most
of the stands were open-grown with mean basal areas < 10 m2/ha. All stands
were infested with the spruce budworm but their populations were declining.

Spider taxa. — Spiders of 10 families, 17 genera, and at least 22 species were
collected from foliage of balsam fir and red spruce in east-central Maine (Table
1). Despite unequal sample sizes (balsam fir, N = 343 branches; red spruce, N =
270 branches), the species of spiders were distributed about equally between tree
species, i.e., balsam fir, 19 species; red spruce, 20 species. However, web-spinning
species were more prevalent among branch samples for both balsam fir (63.2%)
and red spruce (70.0%). These observed species compositions did not differ
significantly (P > 0.05) from the expected proportions (Jennings and Dimond
1988) for either tree species (balsam fir, G = 0.28; red spruce, G = 0.32).

The number of species per spider family ranged from one (Tetragnathidae) to
five (Araneidae); the latter includes species identified only to generic-level
{Araneus sp., Neoscona sp.).

Spider species composition varied among sites; X = 7.6 ± 1.2 SE, range 3 (SH)
to 12 (DL, MR), where N = 8 sites. Only one species, Grammonota angusta
Dondale, was common to all eight study sites sampled in 1987. Dictyna
brevitarsus Emerton, Theridion sp., Philodromus sp. {rufus grp.), and
Metaphidippus flaviceps Kaston were each found on seven sites. Five species
represented by adult spiders, Ceraticelus atriceps (O. R-Cambridge),
ERIGONIDAE undet. female, Cyclosa conica (Pallas), Mangora placida (Hentz),
and Eris militaris (Hentz), were each found on only one study site.

Spider numbers, life stages, sex ratios. — Despite the unequal distribution of
branch samples between tree species, over half (55.9%) of the total sampled
spiders {N = 315) were from red spruce. Most of the collected spiders (13 lost, N
— 302, Table 1) were females (47.4%), followed by juveniles (44.0%) and males
(8.6%). Distributions of spider life stages for each tree species were: balsam fir —
juveniles (41.5%), males (12.6%), females (45.9%); red spruce — juveniles (46.1%),

JENNINGS ET AL.— SPIDER-BUDWORM DENSITIES

185

Table 1. — Spiders on foliage of Abies balsamea and Picea rubens , east-central Maine, 1987.

FAMILY

Balsam fir

Red spruce

Species

Male

Female

juv.

Male

Female

juv.

WEB SPINNERS

DICTYNIDAE

Dictyna brevitarsus Emerton

Dictyna phylax Gertsch & Ivie

Dictyna sp.

THERIDIIDAE

Theridion differens Emerton

Theridion murarium Emerton

Theridion sp.

LINYPHIIDAE

Pityohyphantes costatus (Hentz)

Pityohyphantes sp.

ERIGONIDAE

Ceraticelus atriceps (O. P. -Cambridge)

Grammonota angusta Dondale

Grammonota pictilis (O. P.-Cambridge)

Grammonota sp.

Undet. sp.

ARANEIDAE

Araniella displicata (Hentz)

Araniella sp.

Araneus sp.

Cyclosa conica (Pallas)

Mangora placida (Hentz)

Neoscona sp.

TETRAGNATHIDAE

Tetragnatha sp.

Subtotals

HUNTERS

CLUBIONIDAE

Clubiona trivialis C. L. Koch

Clubiona sp.

PHILODROMIDAE

Philodromus exilis Banks

Phiiodromus pernix Blackwall

Philodromus placidus Banks

Philodromus sp. ( aureolus grp.)

Philodromus sp. ( rufus grp.)

THOMISIDAE

Xysticus punctatus Keyserling

Xysticus sp.

SALTICIDAE

Eris militaris (Hentz)

Eris sp.

Metaphidippus flaviceps Kaston

Metaphidippus sp.

Subtotals

TOTALS

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Figure 2. — Frequency distribution of spiders on balsam fir and red spruce branches, east-central
Maine, 1987.

males (5.4%), females (48.5%). Sex ratios of males to females were: balsam fir,
1:3.6; red spruce, 1:9.0; both tree species, 1:5.5. All comparisons of spider sex
ratios were highly biased (P < 0.001) in favor of females: balsam fir, G = 27.2;
red spruce, G = 66.2; both tree species, G = 89.2.

The number of spiders per branch ranged from 0 to 4 for balsam fir; from 0 to
8 for red spruce (Fig. 2). Red spruce branches tended to have more spiders/
branch than balsam fir. For example, 17.0% of the red spruce branches ( N = 270)
had 2 or more spiders/ branch, whereas only 7.6% of the balsam fir branches
(N = 343) had 2 or more spiders/ branch.

Spider densities. — For both high- ( > 10 branches/ site) and low- (10 branches/
site) intensity samplings of balsam fir, spider populations/ m2 of foliage area
varied among study sites (Table 2, column 2fs). However, spider populations/ m2
of red spruce foliage did not differ significantly among study sites regardless of
sampling intensity.

Spider densities generally were greater on red spruce than on balsam fir (Table
2, row 2Ts); overall, these differences were significantly greater for the high-
intensity sites sampled in 1987. Conversely, overall spider densities were not
significantly different between tree species for the low-intensity sites.

Spider densities also varied by sampling date (Fig. 3). Mean densities on red
spruce trees exceeded those on balsam fir trees 10 out of 14 sampling dates. For
both tree species, mean densities generally declined as the season progressed.

Budworm densities. — Densities of spruce budworm larvae and pupae/ m2 of
foliage also varied among study sites for both tree species (Table 3, column 2Ts).
For high-intensity sites, overall mean_ densities were not significantly different
between tree species (Table 3, row JTs). However, for low-intensity sites, the
overall mean density was significantly greater on balsam fir than on red spruce.

Spider-budworm density relationships. — Spider and spruce budworm densities
covaried among study sites for each tree species; however, most of the
correlations were weak ((rho) < 0.30) and many were nonsignificant (P > 0.05),
especially for low-intensity sites. Over all sites and sampling intensities, there was

JENNINGS ET AL.— SPIDER-BUDWORM DENSITIES

187

Table 2. — Densities of spiders/m2 of balsam fir and red spruce foliage, east-central Maine, 1987.
Within each sampling group (high-low), column means (ab, a'b'), and row means (xy) followed by the
same letter(s) are not significantly different, SAS Institute (1985), Kruskal- Wallis Test, P = 0.05. * =
MA classed as both high- and low-intensity site.

Spiders X (± SE) / m2 of foliage

1987 No. branches No. branches

Sites sampled Balsam fir sampled Red spruce

HIGH-INTENSITY SITES

11.5 acx

(3.6)

10.3 ax

(2.2)

9.8 ax

(1.6)

13.9 ax

(2.7)

6.0 bcx

(1.6)

9.8 ax

(2.5)

5.4 bcx

(1.6)

13.5 ay

(3.0)

MA*

4.4 b

(1.2)

All

313

7.2 x

(0.9)

229

12.0 y

(1.3)

LOW-INTENSITY SITES

14.8 a'x

(4.4)

18.4 a'x

(5.5)

13.3 a'b'x

(5.3)

9.2 a'x

(4.3)

3.0 b'x

(2.2)

10.3 a'x

(4.2)

MA*

17.6 a'

(5.5)

All

10.4 x

(2.5)

13.8 x

(2.4)

little difference between tree species; balsam fir ((rho) = 0.17, P = < 0.01, N =
343), red spruce ((rho) = 0.15, P = 0.01, N= 270).

DISCUSSION

Spider taxa. — The species of spiders we collected from foliage of balsam fir and
red spruce are typical arboreal spiders of northeastern spruce-fir forests. All of
the identified species collected during this study previously have been taken from
coniferous-tree foliage in east-central Maine (Jennings and Dimond 1988). Many
of the same species also have been found on red spruce foliage in northern Maine
(Jennings and Collins 1987). Based on their relative abundance, species common
to arboreal habitats of Maine’s spruce-fir forests include Dictyna brevitarsus
Emerton, Theridion murarium Emerton, Pityohyphantes costatus (Hentz),
Grammonota angusta Dondale, Araniella displicata (Hentz), Clubiona trivialis C.
L. Koch, Philodromus exilis Banks, P placidus, and Metaphidippus flaviceps
Kaston. Five of these species — D. brevitarsus, G. angusta, P. exilis, P placidus,
and M. flaviceps — comprised 46.0% of all collected spiders in this study.

Apparently, none of the commonly collected species exhibited a definite habitat
preference for either tree species; their relative abundances were about the same
on balsam fir and on red spruce. The salticid, M. flaviceps, was slightly more
abundant on balsam fir (Table 1), which is consistent with our earlier study
(Jennings and Dimond 1988). We conclude that the erigonid, G. angusta, is much
more prevalent on foliage of balsam fir and red spruce than its congeneric, G.
pictilis (O. P.-Cambridge). Loughton et al. (1963) reported that G. pictilis was one
of the most abundant spiders on balsam fir foliage at Fredericton, New
Brunswick; however, according to Dondale (1959), most early collections and
identifications of Grammonota in the Northeast refer to G. angusta, not G.
pictilis.

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THE JOURNAL OF ARACHNOLOGY

25-1

SAMPLING DATE

Figure 3. — Mean density of spiders/ m2 of foliage by sampling date, balsam fir and red spruce, east-
central Maine, 1987.

Our observed differences in spider species composition by foraging strategy
(web spinner, hunter) are consistent with earlier findings (Jennings and Dimond
1988; Loughton et al. 1963). The arboreal spider fauna of northeastern spruce-fir
forests is dominated by the web-spinner guild, chiefly species of Erigonidae and
Araneidae. The arboreal hunter guild in these forests consists mainly of species of
Philodromidae, Thomisidae, and Salticidae.

Spider numbers, life stages, sex ratios. — Our results for these parameters
complement and support earlier findings (Jennings and Dimond 1988), namely
that: (1) more spiders are found on foliage of red spruce than on foliage of
balsam fir; (2) for both tree species, spider individuals are distributed unevenly
among life stages (juveniles, males, females); and (3) for both tree species, spider
sex ratios (malesTemales) are biased in favor of females. No doubt, some of the
observed differences in spider numbers, life stages, and sex ratios can be
attributed to the reproductive cycles, developmental periods, and survivorships of
individual species. For example, our sampling period spanned the time when both
juveniles and adults of biennial species were present (e.g., Philodromus placidus
and Xysticus punctatus Keyserling, see Dondale 1961, 1977). Because female
spiders generally live longer than male spiders (Gertsch 1979), a biased sex ratio
in favor of females can be expected. However, this does not fully explain the
greater disparity in spider sex ratios on red spruce (1:9.0) as compared to balsam
fir (1:3.6) that we observed in 1987. Because of the dense, closely compact foliage
of red spruce, we suspect that resident female spiders gain some measure of
protection from foliage-searching predators. If so, such females would have
greater survival than their conspecifics on balsam fir, which has relatively open,
flat foliage.

Spider-budworm densities. — The spider densities observed in 1987 generally are
lower than those previously recorded (Jennings and Dimond 1988). For example,
the mean overall density for balsam fir was 10.9 spiders/m2 of foliage in 1985,
and 8.5 spiders/m2 in 1986 (Jennings and Dimond 1988); and 7.2 spiders/m2 in

JENNINGS ET AL.— SPIDER-BUDWORM DENSITIES

189

Table 3. — Densities of spruce bud worms/ m2 of balsam fir and red spruce foliage, east-central
Maine, 1987. Within each sampling group (high-low), column means (ab, a'b'), and row means (xy)
followed by the same letter(s) are not significantly different, SAS Institute (1985), Kruskal-Wallis Test,
P = 0.05. * - M A classed as both high- and low-intensity site.

Spruce budworms X (± SE) /m2 of foliage

1987 No. branches No. branches

Sites sampled Balsam fir sampled Red spruce

HIGH-INTENSITY SITES

169.0 ax

(22.6)

79.0 by

( 9.6)

139.2 ax

(13.1)

123.2 ax

(13.2)

46.4 bx

( 9.3)

19.1 cy

( 4.5)

21.6 bx

( 3.9)

13.3 cy

( 4.2)

MA*

9.9 c

( 2.4)

All

313

73.9 x

( 6.5)

229

60.5 x

( 5.4)

LOW-INTENSITY SITES

340.1 a'x

(51.3)

237.9 a'x

(43.1)

83.9 b'x'

(30.8)

26.9 b'x

( 9.9)

80.8 b'x'

(14.6)

69.0 bx

(24.7)

MA*

27.9 b'

(11.7)

All

168.2 x

(30.0)

89.9 y

(18.4)

1987 (Table 2). Similarly, for spruces (red and white), mean overall density was
16.3 spiders/m2 in 1985 (Jennings and Dimond 1988); and, for red spruce, only
12.0 spiders/m2 (high-intensity sites) and 13.8 spiders/m2 (low-intensity sites) in
1987 (Table 2). Spruces were not sampled in 1986. We suspect that these declines
in spider populations can be attributed to similar declines in potential prey
populations (i.e., spruce budworms) in east-central Maine. Mean overall densities
of spruce budworms generally were greater than 100/m2 of foliage in 1985 and
1986 (Jennings and Dimond 1988); however, in 1987, similar densities usually
were less than 100/m2 of foliage (Table 3).

Despite individual site differences, our observations in 1987 further indicate
that red spruce has more spiders than balsam fir. This conclusion is supported by
the between-tree differences for overall site means (Table 2, red spruce, X = 12.0
spiders/m2; balsam fir, X = 7.2 spiders/m2; Kruskal-Wallis x2 = 7.7, P — 0.005),
and by the number of sampling dates (10 out of 14, Fig. 3) that mean spider
densities on red spruce exceeded those on balsam fir. Nevertheless, sampling
intensity affected these population-density estimates because between-tree
differences were not detected Jor the low-intensity sites (Table 2, red spruce, X =
13.8 spiders/ m2; balsam fir, X = 10.4 spiders/ m2; Kruskal-Wallis x2 = 0.89, P =
0.35). For future between-tree comparisons of spider densities, we recommend
that trees be sampled over several dates and with sample sizes > 10 branches/ tree
species. Large sample sizes should help to stabilize variances within tree species
and among study sites.

Spider-budworm relationships. — Our observations in 1987 further indicate that
spiders may have been responding to available prey (budworm) populations in
east-central Maine. This conclusion is supported by the fact that both spider and
budworm populations generally declined together over the 3-year period, 1985-87,
(this study; Jennings and Dimond 1988). Although the possible effects of density-
independent factors (e.g., weather) on these populations cannot be ruled out, we

190

THE JOURNAL OF ARACHNOLOGY

suspect that declines in budworm population densities concomitantly affected
spider populations in a density-dependent fashion. However, more detailed
studies are needed before we can fully understand spider-budworm interactions
and their possible population density-relationships. Apparently, the weak
correlations between spider-budworm densities/m2 of foliage area observed during
this study are to be expected; similar weak correlations were observed for spider-
budworm densities on red spruce foliage in northern Maine (Jennings and Collins
1987).

Interestingly, individuals and species of all three spider families (Erigonidae,
Theridiidae, Salticidae) previously identified as potentially important in spruce
budworm dynamics (Loughton et al. 1963) were common among foliage samples
taken from balsam fir and red spruce in east-central Maine. Future studies of
spider-budworm interactions should concentrate on abundant species like
Grammonota angusta, Theridion murarium, and Metaphidippus flaviceps.
Because of their frequencies in coniferous-tree samples, relative abundances, and
active foliage-searching behaviors, species of Thomisidae and Philodromidae also
are likely predators of spruce budworm larvae. In laboratory feeding trials
(Jennings, unpubl.), Xysticus punctatus readily accepted and fed on late instars
(L5 - Le) of the spruce budworm. The predatory habits of this thomisid spider
that frequents coniferous-tree foliage (Dondale and Redner 1978) warrant further
investigation.

Spider-tree relationships. — Why does red spruce have more spiders/ m2 of
foliage area than balsam fir? Stratton et al. (1979) attributed the greater spider
diversity on white spruce foliage, as compared to that on foliage of red pine and
northern white-cedar, to differences in plant physiognomy. We suspect that
differences in foliage shape, structure, and density (number of needles per
internode) also influence arboreal spider populations on red spruce and balsam
fir. The availability of suitable habitat structures can limit spider population
numbers (Riechert and Gillespie 1986); hence, the open, relatively flat needles of
balsam fir probably provide less microhabitat space for web-spinning and
foraging than the compact, curved needles of red spruce.

In Sweden, Gunnarsson (1988) found that percentage needle loss affected
population densities of spiders on Norway spruce, Picea abies (L.). The density of
large spiders (length > 2.5 mm) was about twice as great in a stand with low
needle loss as that in a stand with high needle loss. Because spiders are easier to
detect on branches with few needles, Gunnarsson (1988) postulated that large
spiders might be more vulnerable to bird predation.

Similarly, in the spruce-fir forests of Maine, defoliation by the spruce budworm
could adversely affect resident spider populations on balsam fir, red spruce, and
other host-tree species. Balsam fir is extremely sensitive to defoliation by the
spruce budworm (Witter et al. 1984), and balsam fir usually receives more feeding
damage and is more vulnerable to mortality than red spruce (Blum and Mac Lean
1984). Although we did not measure tree or branch defoliation during this study,
balsam fir branches generally had fewer needles and more budworm feeding
damage than red spruce. Such differences in foliage quantity may have
contributed to the lower spider densities that we observed on balsam fir.

Pest management implications. — Results of this and our earlier study (Jennings
and Dimond 1988) confirm that balsam fir generally has fewer spiders/ m2 of
foliage area than red spruce. Balsam fir is the principal host of the spruce

JENNINGS ET AL.— SPIDER-BUDWORM DENSITIES

191

budworm in eastern North America (Miller 1963); it is the tree species most
severely damaged by the spruce budworm (Kucera and Orr 1981). The spruces—
white, red, and black ( Picea mariana) — on the other hand, are less vulnerable to
damage by the spruce budworm (Blum and MacLean 1984). Forest entomologists
have long attributed this relative “immunity” of spruces to host-insect
asynchrony. The emergence of young budworm larvae from overwintering
hibernacula in the spring may precede budbreak of spruces by several days;
consequently, the larvae are forced to feed on old, less nutritious foliage (Morris
et al. 1956; Greenbank 1963). Because balsam fir buds burst some 13 days before
red or black spruce (Greenbank 1963), young instars of the spruce budworm are
able to feed on new, nutritious foliage of balsam fir before similar foliage is
available on spruces. These differences in host-foliage phenologies affect
budworm survival and subsequent tree damage (Morris 1963; Greenbank 1963).
However, based on our findings, we suggest that abundant spider populations
also contribute to the apparent “immunity” of spruces to damage by the spruce
budworm. If true, then management of forest stands to favor spruces over balsam
fir may provide an indirect, cultural method to enhance these natural enemies of
the spruce budworm.

But, can spider populations be enhanced or increased indirectly through
silvicultural treatments designed to favor spruces over balsam fir? We believe that
they can, because habitat-structural features are important determinants of spider
populations (Riechert and Lockley 1984; Riechert and Gillespie 1986; Riechert
and Bishop 1990). Silvicultural methods and guidelines are already available for
increasing species composition and basal areas of spruces in northeastern spruce-
fir forests (Frank 1979, 1985; Frank and Blum 1978). Such silvicultural
treatments are advocated as a means to minimize forest-stand vulnerability to
budworm damage (Blum and MacLean 1984). We predict that forest-stand
treatments designed to favor spruces will also have a positive influence on
resident spider populations through increases in favorable habitat structure. Our
prediction needs to be tested by carefully designed and controlled experiments
where both spider and potential prey densities are monitored before and after
silvicultural treatments. Such information is needed before the onslaught of the
next spruce budworm epidemic, which is expected in 25 or 35 years (Blais 1983;
Royama 1984; Eidt 1989). Because of potential adverse impacts on prey diversity
for spiders (Provencher and Vickery 1988), monocultures of red spruce, or any
other conifer, should be avoided. Diversification of coniferous-tree habitats in
northeastern spruce-fir forests is much more desirable and ecologically sound.

ACKNOWLEDGMENTS

We are grateful to T. A. Skratt for technical and computer programming
assistance. R. A. Hosmer provided consultative programming assistance; J. J.
Melvin provided word processor service; and M. J. Twery provided computer
graphics. Constructive reviews of an early draft were given by C. D. Dondale, M.
H. Greenstone, S. E. Riechert, and K. V. Yeargan. D. W. Seegrist, Northeastern
Forest Experiment Station, Broomall, PA, provided statistical review. This
research was supported by the USDA Forest Service, Northeastern Forest
Experiment Station, RWU-4151, Orono, ME, and by the Department of
Entomology, University of Maine, Orono, ME.

192

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Blum, B. M. and D. A. MacLean. 1984. Silviculture, forest management, and the spruce budworm.
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tech, coords.). USDA Agric. Handb. 620, 192 pp.

Dondale, C. D. 1959. Definition of the genus Grammonota with descriptions of seven new species.
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Dondale, C. D. 1961. Life histories of some common spiders from trees and shrubs in Nova Scotia.
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Hormiga, G. and H. G. Dobel. 1990. A new Glenognatha (Araneae, Tetragnathidae) from New Jersey,
with redescriptions of G. centralis and G . minuta. J. Arachnol., 18:195-204.

A NEW GLENOGNATHA (ARANEAE, TETRAGNATHIDAE)
FROM NEW JERSEY, WITH REDESCRIPTIONS OF
G. CENTRALIS AND G. MINUTA

Gustavo Hormiga1*2 and Hartmut G. Dobel1

'Department of Entomology
University of Maryland
College Park, Maryland 20742 USA

and

department of Entomology
National Museum of Natural History
Smithsonian Institution

Washington, DC 20560 USA

ABSTRACT

Both sexes of the tetragnathid spider Glenognatha heleios n. sp. are described and illustrated. Data
about its natural history, ecology and phenology are included. A key to the Glenognatha species north
of Mexico is presented. The types of two other Glenognatha species, G. centralis Chamberlin, 1925
and G. minuta Banks, 1898, from Panama and Baja California respectively, are redescribed and
illustrated.

INTRODUCTION

The spider genus Glenognatha Simon, 1887 includes 12 named species from

North, Central and South America, and the Caribbean and Galapagos Islands,
but there are also undescribed representatives in tropical America and the Pacific
Islands (Levi 1980; Hormiga unpublished data). Glenognatha species north of
Mexico were revised by Levi (1980). Here both sexes of G. heleios n. sp. are
described and illustrated, and some data on the species’ natural history are
presented. The male of G. centralis Chamberlin, 1925 and G. minuta Banks, 1898
are redescribed to provide adequate illustrations and descriptions because the
original ones were not sufficient for identification purposes. It is not our purpose
to assess or report the full range of the variation of G. centralis and G. minuta
and therefore we did not study material other than the types. This paper is not
meant to be a revision but it may serve as an addendum to Levi’s revision (1980)
of the Glenognatha north of Mexico.

According to the generic redescription given by Levi (1980), Glenognatha
species have three teeth on the anterior margin of the chelicerae and four on the
posterior. However we have examined specimens of an undescribed species from
Venezuela that have five or six teeth on the anterior margin of the chelicerae and

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six or seven on the posterior; these specimens also possess the pleural bars
between coxae I-II and II-III, a character not common in Glenognatha (e.g.,
present in G. mira Bryant, 1945 between coxae II-III). These data suggest that the
study of new species may add some changes to the diagnosis and description of
Glenognatha.

METHODS

Specimens were examined and illustrated using a Wild M-5® stereoscopic
microscope with a Wild 1.25X camera lucida; further details were studied using a
Leitz Ortholux II® compound microscope. Female genitalia were cleaned by
means of trypsin digestion after removal with sharpened needles. The male and
female genitalia were mounted in Hoyer’s medium on a microscope slide.
Measurements are given in mm. Tarsal length of the male palp is given as the
length of the cymbium. The left palp is illustrated, if not otherwise stated.
Abbreviations used in the text are standard for Araneae.

The research on the ecology of G. heleios was conducted in an extensive
intertidal marsh in the Mullica River — Great Bay estuarine system where Great
Bay Boulevard crosses over Little Thorofare Creek near Tuckerton, Ocean
County, New Jersey. G. heleios was sampled in habitats dominated by Spartina
alterniflora Lois., the salt marsh cordgrass, which occurs in three distinct growth
forms over an elevational gradient from 1.5 m below mean high water level to
mean high water level (Redfield 1972). On the low marsh tall form S. alterniflora
(50 to more than 200 cm tall) grows with reduced culm density along tidal creeks
and bay edges (Adams 1963; Blum 1968). Further up the elevational gradient the
tall form of S. alterniflora grades into stands of an intermediate growth form (SO-
SO cm tall) with an increased culm density (Niering and Warren 1980). On the
high marsh near mean high water level, short form S. alterniflora (10-30 cm tall)
grows at high densities. A more detailed description will be published elsewhere
(Ddbel et al. in prep.).

Two study plots (each 100 m1 2 and separated by > 100 m) were established in
each of the three Spartina habitats. On a bi-weekly basis from early May until
late October, 1985 (11 dates in all), four samples were taken from each plot with
a D-Vac® suction sampler (Dietrick 1961). Each sample consisted of four, 15
second random placements of a D-Vac® sampling head (0.0929 m2) on the
vegetation surface. Arthropods were killed with ethyl acetate and transferred into
jars containing 90% ethanol. Spiders were sorted to species and age class (adults
and immatures) and counted.

Levi’s key to the Glenognatha north of Mexico (Levi 1980) is modified as
follows to include G. heleios (figures 255-289 and map 8 refer to his cited work):

1. Less than 3.0 mm total length; female with chelicerae not enlarged (fig. 272;
Fig. 13); male with spur on chelicerae (figs. 276, 285; Figs. 5-8); embolus
and conductor minute on huge spherical tegulum (figs. 278, 287; Figs. 9-11);

southern Canada to Central America and West Indies (map 8) .2

Total length more than 3.5 mm; female with chelicerae enlarged (fig. 255);
male without spur on chelicerae (fig. 266); embolus and conductor length
greater than height of spherical tegulum (fig. 268); New Mexico, Arizona
(map 8) emertoni

HORMIGA & DOBEL— A NEW GLENOGNATHA FROM NEW JERSEY

197

Figures 1, 2. — Glenognatha heleios n. sp.: 1, subadult male; 2, web (web diameter about 10 cm).

2. Paracymbium with a tooth in its anterior margin (Fig. 9); male with hooked

tooth on anterior margin of chelicerae (Figs. 5-8); tip of the embolus not

coiled (Figs. 9-11); New Jersey .heleios

Paracymbium without a tooth in its anterior margin ........ 3

3. Female unknown; male with hooked tooth on anterior margin of chelicerae

(fig. 285); tip of embolus coiled (fig. 289); Mississippi (map 8) iviei

Male without hooked tooth on anterior margin (fig. 276); tip of embolus not
coiled (fig. 280); southern Canada to Central America, West Indies (map 8)
./ox/

Glenognatha heleios , new species
Figures 1-17

Types. — Male holotype, four male paratypes and three female paratypes from
New Jersey, Ocean Co., Tuckerton; collected on Spartina alterniflora in a lightly
flooded salt marsh; 7 Nov. 1984 (8-1) (H. Dobel col.). Eight male and eight
female paratypes from the same locality; 9 Oct. 1984 (8-2) (H. Dobel col.).
Deposited in USNM; paratypes are also deposited in AMNH and MCZ. For
nomenclatural purposes the senior author should be considered the author of the
species description.

Etymology. — The specific epithet is from the Greek helos (marsh, meadow),
hence heleios dwelling in a marsh, and refers to the known habitat of this species.

Diagnosis. — Glenognatha heleios differs from G. iviei Levi, 1980 in the shape
of the paracymbium and the presence of a tooth on its anterior margin (Fig. 9).
The larger body size and the shape of the hooked tooth on the chelicerae also
separate G. heleios from G. iviei (Figs. 5-8).

Description. — Male (Holotype). Total length 2.04. Cephalothorax 1.03 long,
0.87 wide, 0.65 high. Sternum 0.50 long, 0.53 wide. Abdomen- 1.25 long, 1.06
wide, 0.93 high. AME diameter 0.063; eyes of equal diameter; AME separation
1.25 times their diameter, PME separation 1.25 times their diameter; ALE, PLE
juxtaposed; PME PLE separation 1.75 times one PME diameter. Clypeus height
3.5 times one AME diameter. Chelicerae large (Figs. 5-8), four prolateral and
four retrolateral teeth. Cephalothorax, chelicerae, sternum and legs light brown.
Abdomen (Fig. 3, 4), dorsum light gray with black and white dorsal marks;

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Figures 3-11. — Glenognatha heleios n. sp.: 3-5, holotype male; 3, dorsal; 4, ventral; 5, eye region
and chelicerae; 6-8, left chelicera of male paratype; 6, distal portion, ectal; 7, posterior; 8, anterior; 9-
11 palp of holotype male; 9, mesal; 10, posteroectal; 11, ectal. Abbreviations: C = conductor; CY
cymbium; E = embolus; P = paracymbium; T = tegulum. Scale bars: 0.5 mm for Figs. 3-8, 0.25 mm
for Figs. 9-11.

HORMIGA & DOBEL— A NEW GLENOGNATHA FROM NEW JERSEY

199

Figures 12-14. — Glenognatha heleios n. sp., paratype female; 12, dorsal; 13, eye region and
chelicerae; 14, genitalia, dorsal. Scale bars: 0.5 mm.

venter dark gray with light marks. Leg and pedipalp lengths of male described
above:

Total

1.12

0.34

1.12

0.87

0.53

3.98

1.03

0.34

0.97

0.81

0.47

3.62

III

0.65

0.28

0.47

0.31

2.18

0.90

0.28

0.78

0.65

0.40

3.01

Pdp

0.47

0.19

0.12

—

0.59

1.37

Legs I>II>IV>IIL Palp (Figs. 9-11).

Female (Paratype). — Total length 2.39. Cephalothorax 0.97 long, 0.84 wide,
0.65 high. Sternum 0.53 long, 0.59 wide. Abdomen 1.56 long, 1.25 wide, 1.25
high. AME diameter 0.063; eyes of equal diameter; AME separation 1.25 times
their diameter, PME separation 1.25 times their diameter; ALE, PLE juxtaposed;
PME-PLE separation 1.25 times one PME diameter. Clypeus height 2.4 times
one AME diameter. Chelicerae (Fig. 13), three prolateral and three retrolateral
teeth. Cephalothorax, chelicerae, sternum and legs light brown. Abdomen (Fig.
12), dorsum light gray with black and white marks, venter dark gray. Leg and
pedipalp lengths of female described above:

Total

1.02

0.31

0.90

0.84

0.50

3.57

0.93

0.31

0.81

0.68

0.47

3.20

III

0.65

0.25

0.43

0.47

0.50

2.30

0.90

0.28

0.68

0.62

0.37

2.85

Pdp

0.31

0.12

0.25

—

0.25

0.93

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Figures 15-17. — Glenognatha heleios, seasonal
abundances at Tuckerton, New Jersey; 15, annual
mean densities (no./m2/yr) in the three Spartina
alterniflora habitats along an elevational gradient.
Means (+ SE, N = 22) with different letters are
significantly different P < 0.05); 16, seasonal
abundance (no./m2) in the three Spartina
alterniflora habitats. Plotted are the means of two
plots for each habitat sampled on 1 1 dates from 7
May to 11 October 1985; 17, seasonal abundance
(no./m2, average across all habitats) of adults and
juveniles. Abbreviations: SAS, short form S.
alterniflora ; SAI, intermediate form S. alterniflora ;
SAT, tall form S. alterniflora.

16 SEASON

SEASON

Legs I>II>IV>III. Vulva (Fig. 14).

Variation. — Male cephalothorax length ranges from 1.00 to 1.15 (n = 13),
females from 0.90 to 1.03 (n — 9). Specimens in alcohol vary in abdominal
pattern, with darker pigmentation of the dorsal pattern and more pronounced
chevron marks in the posterior part of the abdomen; other specimens lack such
marks. The dorsal white silver spots vary in size and number. In some specimens
the abdominal pattern is hardly visible.

Natural history. — In general, G. heleios occurred at rather low densities,
averaging six to eight individuals per m2 each season. This species was most
abundant in short and intermediate form Spartina alterniflora and very rare in
tall form Spartina (Fig. 15). Peak densities of about 25 individuals per m2 were
reached in July/ August (Fig. 16). In New Jersey G. heleios is a univoltine species
producing juveniles from July to August followed by an adult peak in mid-
October (Fig. 17). This species overwinters in the adult stage.

Webs were only found in the short and intermediate form of Spartina
alterniflora where the amount of tidal flooding is very low (<0.5 cm). The web is
located very close to the soil surface (1 to 5 cm) and oriented horizontally. The

HORMIGA & DOBEL A NEW GLENOGNATHA FROM NEW JERSEY

201

sticky spiral is very closely spaced, leaving only minute gaps between two
successive turns of the thread (Fig. 2).

Distribution. — G. heleios has been recorded only from a single locality, an
intertidal salt marsh near Tuckerton, New Jersey where extensive sampling took
place (Dobel et al. in prep.). Nevertheless it is likely that this species also will be
found in other salt marshes with similar habitat structure and climatic pattern.

Material examined.— New Jersey: Ocean Co., Tuckerton; S. alterniflora salt marsh, lightly flooded
(H. Dobel col.); 28 Aug. 1984 (8-4), 3 males; 25 Sep. 1984 (1-2), 2 males; 9 Oct. 1984 (8-4), 3 males; 7
Nov. 1984 (14-1), 4 males, 2 females; 7 Nov. 1984 (8-2), 3 males, 3 females; 7 Nov. 1984 (14-4), 3
males, 4 females; 1 1 Nov. 1984 (14-4), 4 males, 3 females. Deposited in USNM.

Glenognatha centralis Chamberlin, 1925
Figures 18-24

Glenognatha centralis Chamberlin, 1925: 216 (Male description, not illustrated). Female unknown.

Type. — Male holotype, label states “Glenognatha centralis Chamb. Male
Holotype Panama (B. 1072) R. V. Chamberlin Coll.” Deposited in MCZ,
examined.

Note. — The type material of G. centralis (collected from the stomach of a toad,
Bufo sp.) is in bad condition, missing many of the legs and the right pedipalp.
The palpal characters are difficult to see because its morphology is distorted,
probably due to the digestion process. The embolus is missing. We are not even
sure whether the type material represents an adult or is a subadult before the last
molt. After comparison with other Panamanian Glenognatha from the MCZ
collection we have not found any specimen that matched G. centralis in any
characters known to be useful for species diagnosis in Glenognatha. Therefore the
description and diagnosis has to be based on this single specimen until new
specimens are available for study.

Diagnosis. — G. centralis chelicerae (Fig. 19) are much more divergent than
those of the other Central and North American species, and this divergence does
not seem to be an artifact of preservation. The tegulum appears to be smaller
than in other species of Glenognatha and the conductor shape seems unique to
this species, being more elongated and its position more apical (Figs. 22-24).

Description. — Male (Holotype). Cephalothorax 0.97 long, 0.81 wide, 0.81 high.
Sternum 0.53 long, 0.59 wide. AME diameter 0.156; eyes of equal diameter; AME
separation one time their diameter, PME separation one time their diameter;
ALE, PLE juxtaposed; PME-PLE separation 1.4 times one PME diameter.
Clypeus height 2.2 times one AME diameter. Chelicerae large and strongly
divergent (Figs. 19-20), three prolateral and four retrolateral teeth.
Cephalothorax, chelicerae and sternum brownish, legs slightly lighter. Leg and
pedipalp lengths of male described above:

Ill

0.78

0.28

0.59

—

1.09

0.34

0.87

—

Pdp

0.56

0.22

—

0.40

Palp (Figs. 22-24).

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Figures 18-24. — Glenognatha centralis Chamberlin, holotype male; 18, carapace, dorsal; 19, eye
region and chelicerae; 20, left chelicera, ventral; 21, sternum and coxae; 22-24, palp; 22, dorsal; 23,
ectal; 24, ventral. Scale bars: 0.5 mm for Figs. 18-20; 0.25 mm for Figs. 22-24.

Distribution. — Only known from Panama (locality not specified in the label).
Material examined. — Only the holotype.

Glenognatha minuta Banks, 1898
Figures 25-30

Glenognatha minuta Banks, 1898: 248, pi. XV, fig. 15 (male lateral view and chelicera), female
unknown.

Type. — Male syntype, labels state “Glenognatha minuta Bks Cotype San Jose
del Cabo, Baja Calif. Eisen & Vaslit.” and “Nathan Banks Coll.” Deposited in
MCZ.

Note. — G. minuta was described after two specimens, but no holotype was
designated. The syntype series belonged to the California Academy of Sciences
although Banks kept duplicate specimens. After the destruction of the specimens
at the California Academy of Sciences during the earthquake in 1906 only the

HORMIGA & DOBEL— A NEW GLENOGNATHA FROM NEW JERSEY

203

«— — I E — H

Figures 25-30. — Glenognatha minuta Banks, syntype male; 25, dorsal; 26, eye region and chelicerae;

27, left chelicera, ventral; 28, sternum and coxae; 29, 30, palp; 29, mesal; 30, dorsoectal. Scale bars:
0.5 mm for Figs. 25-28; 0.25 mm for Figs. 29, 30.

duplicates have been available for study (Levi, pers. comm.). Therefore, although
only one specimen survived, it should be considered as syntype. It does not seem
appropriate to designate a lectotype.

Diagnosis. — G. minuta differs from other Glenognatha species in the shape of
the embolus and the conductor (Figs. 29, 30). It also differs from other North
American species by the cheliceral teeth (Fig. 26, 27).

Description.— Male syntype. Total length 2.28. Cephalothorax 1.15 long, 0.90
wide, 0.87 high. Sternum 0.56 long, 0.62 wide. Abdomen 1.37 long, 1.19 wide,
1.15 high. AME diameter 0.095; PME 0.83, PLE 0.83, ALE 0.83 times one AME
diameter; AME separation one time their diameter, PME separation 1.4 times
their diameter; ALE, PLE juxtaposed; PME- PLE separation 1.8 times one PME
diameter. Clypeus height two times one AME diameter. Chelicerae large (Figs.
26, 27), three prolateral and four retrolateral teeth. Cephalothorax, chelicerae and
sternum red-brown, legs light brown. Abdomen very light brown, no pattern
visible. Leg and pedipalp lengths of male described above:

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1.56

0.56

1.53

—

1.50

0.34

—

III

1.03

—

1.37

0.31

1.09

—

Pdp

0.59

0.22

—

0.56

Palp (Fig. 29-30).

Distribution. — Recorded from Baja California (San Jose del Cabo, type
locality). Bryant (1940:358) misid entitled a specimen from Cuba as G. minuta.
The Cuban specimen belongs to. a different species which has a longer embolus,
thinner at its end and more curved. Its paracymbium is also different as Bryant
noticed, with the basal part being wider than in the type specimen.

Material examined. — Only the syntype.

ACKNOWLEDGMENTS

Type material and other specimens were kindly provided by the following
curators and institutions (acronyms in parentheses): J. A. Coddington, National
Museum of Natural History, Smithsonian Institution (USNM); H. W. Levi,
Museum of Comparative Zoology, Harvard University (MCZ) and N. I. Platniek,
American Museum of Natural History (AMNH). We are also grateful to J. A.
Coddington for helpful comments and constructive criticism, and to H. W. Levi
and C. Mitter for reviewing an earlier draft of this paper.

LITERATURE CITED

Adams, D. A. 1963. Factors influencing vascular plant zonation in North Carolina salt marshes.
Ecology, 44:445-456.

Banks, N. 1898. Arachnida from Baja California and other parts of Mexico. Proc. California Acad.
Sciences, Third Ser., vol. I (7):205-308.

Blum, J. L. 1968. Salt marsh spartinas and associated algae. Ecol. Monogr., 38:199-221.

Bryant, E. B. 1940. Cuban spiders in the Museum of Comparative Zoology. Bull. Mus. Comp. ZooL,
86 (7):247-554.

Chamberlin, R. V. 1925. Diagnoses of new American Arachnida. Bull. Mus. Comp. ZooL, 67:211-248.
Dietrick, E. J. 1961. An improved back pack motor fan for suction sampling of insect populations. J.
Econ. Entomol., 54:394-395.

Dobel, H. G., R. F. Denno and J. A. Coddington. (In prep.) Spider community structure in an
intertidal salt marsh: effects of vegetation structure and tidal flooding.

Levi, H. W. 1980. The orb - weaver genus Mecynogea , the subfamily Metinae and the genera
Pachygnatha, Glenognatha and Aziiia of the subfamily Tetragnathinae north of Mexico (Araeeae:
Araneidae). Bull. Mus. Comp. ZooL, 149 (1): 1-75.

Niering, R. S. and W. A. Warren. 1980. Vegetation patterns and processes in New England salt
marshes. BioScience, 30:301-307.

Redfield, A. C. 1972. Development of a New England salt marsh. Ecol. Monogr., 42:201-237.

Manuscript received November 1989, revised February 1990.

Eberhard, W. G. 1990. Early stages of orb construction by Philoponella vicinia , Leucauge mariana,
and Nephila clavipes (Araneae, Uloboridae and Tetragnathidae), and their phylogenetic
implications. J. Arachnol., 18:205-234.

EARLY STAGES OF ORB CONSTRUCTION
BY PHILOPONELLA VICINA ,

LEUCA UGE MARIANA , AND NEPHILA CL A VIPES
(ARANEAE, ULOBORIDAE AND TETRAGNATHIDAE),
AND THEIR PHYLOGENETIC IMPLICATIONS

William G. Eberhard

Smithsonian Tropical Research Institute
and

Escuela de Biologia, Universidad de Costa Rica
Ciudad Universitaria, Costa Rica

ABSTRACT

The uloborid Philoponella vicina differs from the araneoids Nephila clavipes and Leucauge mariana
in one movement made during frame construction, in the ordering of frame construction, in proto-hub
removal, and in the highly ordered sequence of operations on adjacent radii just before proto-hub
removal. Data from other uloborids suggest that all of these differences may distinguish orb weaving
uloborids in general from orb weaving araneoids. N. clavipes differs from the other two species in the
order of lines laid during frame construction, in the high variability in the details of frame
construction, and in its failure to remove recently laid lines during exploration, radius construction,
and frame construction. Frame construction behavior in all three species is more variable than
previous reports indicated, and more variable than behavior in later stages of orb construction. In all
three species earlier frame construction more often involves breaking lines already present in the web.

Similarity between uloborid and araneoid frame construction is more likely to be due to a
combination of constructional constraints and inheritance of ancient spinning patterns than previously
realized; it is not clear whether or not it constitutes a synapomorphy uniting the two groups. The
failure of N. clavipes to remove recently laid lines during exploration, radius construction, and frame
construction is probably plesimorphic. Secondary loss of removal behavior seems unlikely because
removal probably confers adaptive advantages. Removal behavior in these contexts and possibly more
stereotyped frame construction behavior probably evolved independently in uloborids and araneoids.

INTRODUCTION

The question of whether orb webs evolved once or more than once
independently in uloborid and araneoid spiders has long been controversial (see
Coddington 1986a and Shear 1986 for recent reviews, also Kovoor and Peters
1988). Perhaps the strongest evidence favoring the single origin hypothesis is that
both the basic construction processes and the sequence in which they occur are
similar in both groups (e.g., Wiehle 1927). Since similarities in later stages of orb
construction could result from the patterns of lines produced during earlier
stages, the earlier stages of orb construction are especially important for
arguments of monophyletic origin. These stages, however, are the least studied
and most poorly understood parts of orb construction behavior.

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Part of the reason for our ignorance is that initiation of orb construction is
more difficult to study than later stages: behaviors are not repeated as many
times per web; lines and attachments are often displaced substantially by
subsequent behavior (e.g., Tilquin 1942), making it difficult for an observer to
maintain an accurate frame of reference; the spiders seem more sensitive to
disturbances (Koenig 1951; Witt et al. 1968; Vollrath 1986); and construction of
the first series of lines often involves long pauses (sometimes over an hour) (Witt
et al. 1968). Arachnologists have had difficulty describing the early stages of web
construction. For instance, there are many published descriptions of frame
construction which are probably simply wrong (McCook, 1889; Kingston 1920;
Comstock 1940; Savory 1952; Levi and Levi 1968; Dugdale 1969; Forster and
Forster 1973; Levi 1978; Foelix 1982 — see Tilquin 1942 and discussion of this
paper); with the possible exception of Tilquin 1942, all other accounts (Peters
1933; Koenig 1951; Mayer 1952; Eberhard 1972; Coddington 1986a) are probably
flawed in ignoring variations.

This paper reports detailed observations of the early stages of web construction
by the uloborid Philoponella vicina (O. Pickard-Cambridge) and the tetragnathids
Leucauge mariana (Kerserling) and Nephila clavipes (Linnaeus). It also gives brief
descriptions of the behavior of four other uloborids, even briefer notes on that of
a variety of other tetragnathids and araneids, and summarizes all published
observations of certain aspects of uloborid behavior which appear to be unique to
this group. The impact of these data on the single vs. multiple origin of orb
controversy is then discussed.

METHODS

P. vicina and N. clavipes normally build between midnight and 0800 hours, so
adult females of P. vicina and nymphs of N. clavipes (probably 2nd-6th instars)
were kept in a small light-tight shed (about 3 X 3 X 2 m) in which lights were
turned on at 1400 hours and shone until 0500. A partially shaded 50 W bulb was
kept burning at all times in order to increase the spiders’ tolerance of light during
the dark phase (Eberhard 1972).

Webs of P. vicina in the field were taped to a 25 cm diameter wire hoop; with
the spider still in place, each was suspended horizontally in the shed. The spiders’
behavior was observed as they built subsequent webs in the hoops. N. clavipes
were induced to build webs on wire frames, which varied from 20-40 cm in
diameter according to the size of the spider, by isolating the spider from contact
with other surfaces by placing the frames in covered pails containing a little
water. Both species were observed by lighting the background with a headlamp
and watching their silhouettes, by shining the headlamp on the spider from the
side and above, or by watching the spider against a surface illuminated by the 50
W bulb. Except when the headlamp shone upward from less than about 20 cm
below the spider (a position avoided during the observations), it seldom caused
overt disturbance of the spider (as indicated by interruption of building, bouncing
on the web, or clear disorientation of behavior).

Observations of N. clavipes were especially difficult to record because the
spiders’ behavior was highly variable, so they were recorded verbally on a tape
recorder, then later transcribed. To avoid startling the spider when I began to
speak, a radio was played softly during the entire building period.

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

207

Mature female L. mariana were kept on horizontal wire hoops in an outdoor
screen cage as described in Eberhard 1987a, and were observed late in the
morning and early in the afternoon while they made their second complete webs
of the day. These spiders moved much more rapidly, but their large size and the
better viewing conditions made detailed observations possible.

The starting point of construction was standardized by cutting away most of
the previous web that was present at the beginning of an observation period,
using a scissors or a hot, fine-tipped soldering iron to leave only three long radial
lines diverging from the web’s previous hub. The mesh lines of N. clavipes outside
the plane of the orb were generally left more or less intact. To assure that P
vicina and L. mariana webs were horizontal, any lines that the spider laid out of
the plane of the hoop were cut just after they were laid.

My observations were somewhat prejudiced against unusual behavior patterns,
because I was unable to record behaviors in which I did not understand the
sequence of line placements and removals; “standard” patterns were easiest to
understand because I could anticipate the spider’s movements. The number of
“standard” behaviors I recognized increased during the study, and toward the end
I was seldom unable to understand any P. vicina aor L. mariana behavior.
However, mesh construction by N. clavipes was so variable and complex that I
was often unable to describe a spider’s behavior, even at the end of the study.
Orb construction in this species was much more stereotyped than mesh
construction, but was still substantially more variable than that of the other
species, and new sequences were seen even at the end of the study.

Construction of over 60 P. vicina webs, 60 L. marina webs and 35 N. clavipes
webs was observed (6 of the N. clavipes webs were small “resting” webs without
sticky spirals). Because I did not note all aspects of building behavior for each
web, separate sample sizes are given for each behavior. In the latter part of the
study I recorded complete lists of the directions and orders of placement of
frames and radii in 17 P. vicina and 18 L. mariana webs, starting observations
soon after the spider began sustained activity. These webs are called “study” webs
in the text. The order of the spider’s operations in each of these webs was later
coded by counting back from the last radius laid in the web; in P. vicina I also
counted the number of behaviors before and after proto-hub replacement. The
position of a given behavior in the entire sequence is indicated in relation to the
total number (TV) of radii laid in the web (i.e., the last radius is 1 / TV, the next-to-
last is 2 /TV, etc.). These fractions probably make some behaviors appear to have
occurred earlier in the construction sequence than they actually did, since the
totals do not include very early behaviors that were followed by long pauses.

The behavior of Uloborus trilineatus (Kerserling) was observed as in P vicina ,
while all other species were observed in the field.

Unless otherwise noted, all statistical tests were made with Chi-squared Tests.
Averages are followed by ± standard deviations. The figures . which describe
behavioral sequences are stylized summaries, and are not to scale. The behaviors
observed are classified (e.g., radius construction, frame construction, mesh
construction) on the basis of the web lines which were laid as a result of the
behavior. Hub construction consisted of laying more or less circular lines at the
hub which were attached to all or nearly all of the radii that were crossed.

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Figure 1. — Web of Philoponella vidua: A, nearly
complete proto-web; B, closeup of the proto-hub,
showing large accumulation of loose silk and lack
of hub lines connecting radii.

RESULTS

Philoponella vicina . — The following sequence summarizes the early stages of
web construction. Initial “exploration” changed more or less gradually into
construction of the radii and frames of the proto-web (Fig. 1). Then the spider
always removed the center of this web ( N = 37) (proto-hub removal or PHR)
reconnecting the radii as it did so (Fig. 2). Following PHR, the spider began
laying hub spiral, and laid more radii and sometimes more frames. These stages
are described in detail below.

I. Exploration : The earliest portions of behavior, corresponding to the
“exploration” stage of Eberhard (1972), were especially difficult to observe and
describe, and I was unable to perceive overall patterns. Several details were the
same as those of U. diver sus (Eberhard 1972). Descents occurred both on the end
of a single line, and while the spider spanned a broken line with its body, reeling
in one broken end while paying out dragline silk that was attached to the other.
Often descents on broken lines began with the spider paying out line faster than it
reeled it in, and ended with it reeling in more rapidly than it paid it out. This
caused the spider to descend through an arc, then climb more or less straight up.
Some descents on single lines were preceded by two to four increasingly deep
descents back and forth on the same radial line, but others were not. Spiders
sometimes descended >50 cm to touch the floor, then immediately reascended the
dragline without making an attachment. The failure to attach suggests that this
behavior functions as exploration. Spanning lines carried on air currents
(Eberhard 1987b) were often initiated on descents, but spiders did not usually
move far from the original website.

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209

Figure 2. Web of P. vicina : A, just after proto-
hub replacement (one radius was laid after the
protohub was removed); B, closeup of hub of this
web. The loose silk is gone, and the radii are
connected by an approximately circular line that
was laid as the loose silk was removed.

Spiders moved lines by breaking them at one end, and spanning the hole while
carrying the broken end to another attachment site (Eberhard 1972). Similar
results were achieved by removing a line entirely and replacing it with a new
dragline that was attached at a different point. Accumulations of silk from
previous webs were sometimes cut free and discarded with waving movements of
legs I; other accumulations were cut free, wrapped for several minutes, and
ingested as described for U. diversus. The reason some silk was discarded is
unclear. Two spiders which dropped an accumulation of silk while removing lines
from previous webs later ingested turfts of newly laid silk at the proto-hubs of the
same webs.

The length of time spent in exploration varied greatly, and activity was often
interrupted by pauses of an hour or more. Eventually several lines were joined
together approximately where the future hub would be (the “proto-hub”) (Fig. 2).
Sometimes there were two such sites of intersection, and one was later removed
or moved and added to the other.

Attachments to the wire rim were generally made on a surface of the wire that
faced somewhat away from the direction of the line itself. This probably results in
a firmer attachment to the substrate, since (other things being equal) the force
exerted by the line on the attachment will be more nearly parallel to the plane of
the attachment (compare the difficulty of pulling an adhesive tape directly off of
a surface versus sliding it along the surface).

II. Frame construction and events leading up to PHR : The behavior
immediately proceeding PHR became less variable. Radial lines were “modified”
in one of three ways: moved; removed partially or completely; or connected by
frames. Two kinds of partial replacements occurred. In the simplest and most
common (124 of 126 cases in which this detail was recorded in the study webs),

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Figure 3. — Two types of partial replacement of radii: Dashed lines with arrows show the route
taken by the spider’s feet, dotted lines are lines already present, intact lines are those newly laid in
each drawing, and large dots mark new attachments. A, the spider breaks and reels up the exit radius
while moving away from the hub (above), then turns and replaces the newly laid dragline by breaking
and reeling on the way back (below); B, the spider leaves the exit line intact as it leaves the hub,
attaches its dragline to the exit on the way out and then moves onward and sideways (above). After
making an attachment to the substrate or other lines, it returns, replacing the newly laid dragline and
its attachments to other lines with another dragline and attachments (below).

the spider broke the exit radius while moving away from the proto-hub as just
described. It stopped part way out the exit, turned 180° and attached the dragline
to the outer broken end, then returned to the hub reeling up the dragline it had
just laid (Fig. 3A). In a few cases (2 in the study webs) the exit radius was left
intact on the trip out, the dragline was attached to it part way out and the spider
continued onward and to the side without breaking the exit line (in one case it
broke other lines it encountered there). After attaching the dragline, the spider
returned to the hub, reeling up and replacing both the exit line and the line that
it had laid on the way out (Fig. 3B).

Spiders also often moved radii by replacing them (56 of 186 cases in which
radii were modified in study webs; 63% of the 56 involved frame construction).
The spider began as if to replace the radius, breaking the line (the “exit radius”)
at the proto-hub or while moving away from the proto-hub and rolling up the
loose silk as it went. It moved all the way to the end of the exit, then moved to
one side along other lines or the wire rim, sometimes cutting other lines in the
vicinity and/or attaching the dragline one or more times to them. Then it
attached the dragline and turned back to return along it to the proto-hub, reeling
up and replacing the newly laid line. The spider attached the new dragline at the
hub, but did not generally make any other attachments before leaving on another
trip away from the hub.

Sometimes (8 times in 17 study webs) the spider added a new radius: it moved

away from the proto-hub without breaking the exit line, and then moved to the

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

211

Figure 4. — Sequence of events in P. vicina frame construction Type A (conventions as in Fig. 3):
Lines already present during a given stage are all represented as being single. Insets here and in later
figures are included to clarify the number of “lines” actually present (in fact, spiders generally lay a
pair or more of lines as they move; each line in the insets represents all of the components of a single
dragline).

side, away from the end of this radius, attached its dragline to the frame line or
wire rim, and returned to the hub along the new radius, breaking it and rolling it
up as it went. This sequence of behavior was identical to the typical radius
construction behavior of araneoids (FI of Eberhard 1982). Addition of radii was
probably more common than the numbers suggest since the very earliest stages of
construction that were followed by long pauses were not counted. One radius
(laid just before PHR) was sealed by the spider on its way to the hub (Fig. 8).

Frame construction behavior varied (types A-E in Figs. 4-8), but several details
showed clear patterns. On the first trip back to the hub spiders sometimes
attached to the exit radius twice instead of once as shown in Fig. 5B. Spiders
always broke the second portion of the new frame line while returning to the new
radius, and always shifted the attachment outward (e g., Fig. 4C) before returning
to the hub ( N = 126) (Figs. 4-8). In four cases the new frame (e.g., the line laid in
Fig. 4C) was slack and the spider reeled in part of the line with its legs IV, thus
tightening it before attaching to the radius. The tuft of loose silk that
accumulated as the spider returned from each frame construction and radius
replacement was left along with other similar tufts at the proto-hub.

Frame construction behavior B (Fig. 5) was most common (44 of 70 cases in
study webs); D (Fig. 7) was next (12 of 70), then A (Fig. 4) (9 of 70), C (Fig. 6)
(3 of 70), and E (Fig. 8) (2 of 70). All A and B frame constructions occurred
before PHR, all D came after PHR (D differs from A and B with respect to
occurrence before or after PHR, P< 0.01); 2 of 3 C occurred before PHR).

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Figure 5. — Sequence of events in P. vicina frame construction Type B (conventions as in Figs. 3 and 4).

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

213

Figure 7. — Sequence of final events in P. vicina frame construction Type D (stages A-C as in Fig. 6)
(conventions as in Figs. 3 and 4).

The impending approach of PHR was signalled when the spider modified radii
(partially or completely replaced them or added frame lines) one after another in
strict sequence moving around the web. An example of such a sequence was a
spider which began this stage with radii at 1,2, 3, 5, 6, 7, 9 and 10:00 positions..
First it modified the 9:00 radius, then, in order, those at 7, 6, 5, 3, 2, 1, and
10:00. In 30 webs in which positions of modified radii were noted, the last five
modifications on radii preceding PHR were all on adjacent radii and all
progressed in a consistent direction except for two cases in which the spider
skipped a single radius.

In addition, when the direction in which a frame line was laid was noted ( N =
50), the frame was always laid so that the exit radius was on the “leading” or far

Figure 8. — Sequence of events in P. vicina frame construction Type E (conventions as in Figs. 3 and

4).

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V/’

^ w ^ (O O h CD O.

FRACTION FINISHED

Figure 9. — Relative numbers of frame lines built at different stages of orb consturction by P. vicina
(dotted line) ( N = 58 frames in 17 orbs) and L. mariana (solid line) ( N = 92 frames in 18 webs) (stage
of construction indicated by fraction of final number of radii already present). Since some
observations began after the first few radii had been laid (inset in Fig. 15), the frames laid in the very
earliest stages (< 0.20) are under-represented.

side of the sector that would be spanned. Thus in the web just mentioned, the
exit on the 9:00 radius resulted in a frame connecting 9 to 10, that on 7 resulted
in a frame from 7 to 9, etc.

The last behaviors preceeding PHR tended to result in smaller modifications of
the web. The last modification before PHR was more likely to be a partial
replacement than a frame construction or radius shift (P < 0.01 comparing last
modification before PHR with preceeding five in 27 webs). In addition, the
partial replacements performed during one or two radial modifications just
preceding PHR ( N = 24 in study webs) more often involved only the inner 20%
portion of the radius’ length than those performed earlier (N = 54) (P < 0.01).

III. Proto-hub removal (PHR): The spider simultaneously cut the accumulation
of loose silk free from where the radii converged, ingested it, and reattached the
radii. In some, but not all cases, the new line joining the radii was nearly circular
(Fig. 2). In 13 webs which had an average of 17.7 ± 4.4 radii when finished, an
average of 7.3 ± 2.1 radii were present when the proto-hub was removed.

IV After PHR: Following PHR, the spider added new radial lines as well as
occasional frames (Fig. 9). Usually the spider chose to exit along the leading edge
of a sector (100 of 127 in 31 webs) as in frame construction preceding PHR, but
in other respects the behavior was quite different. Existing radii were seldom
replaced following PHR (7 of 176 trips from away from the hub in the study
webs). Hub spiral construction after each trip away from the hub began abruptly,
usually and perhaps always starting with the first radius after PHR (occasionally

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

215

it was difficult to be sure of this point for the first new radius or two). All new
radii were added without breaking lines, as described in Eberhard 1972 and 1982
(character F3), and radial lines were continuous with the hub spiral Frame
construction differed from that preceeding PHR; it did not involve breaking
previous lines on the way out from the hub, and it included sealing the break in
the new radius part way back to the hub (types D and E — see Figs. 7 and 8).

Leucauge mariana. — Nothing corresponding to PHR was ever performed by L.
mariana in the early stages of construction. Unless otherwise noted, all data are
from the study webs.

/. Exploration : As with R vicina (and Araneus diadematus — Reed 1968),
preliminary placement and removal of lines prior to construction proper was
generally carried out intermittently over several hours. The same behaviors were
used, including breaking and reeling while replacing lines, shifting attachment
points of lines, descent on single lines (often reaching obects below the web
without making an attachment), and production of airborne spanning lines. The
only exploratory P vicina behavior not performed by L. mariana was wrapping
of accumulated loose silk from the previous web; this difference was not
surprising since the very extensible wet sticky silk of L. mariana contracted
immediately into relatively compact masses on its own when web lines were cut.
L. mariana often made long airborne spanning lines, and was much more likely
to move far from the previous website than was P. vicina. When on lines near the
wire hoop, spiders sometimes bounced up and down as they moved, a behavior
not seen in other situations or in the other species. Possibly this movement serves
to test the rigidity of the substrate.

II. Frame and radius construction : Eventually the spider’s activities became
concentrated around a central point where three or more lines intersected (the
web’s future hub) and the spider repeatedly moved toward the edge and then
returned to this point. Some radii were partially replaced, and new radii as well
as frame lines were laid. Partial radius replacement was like that of P. vicina , and
new radius construction was as described by Eberhard 1982 (character FI).
Frame construction varied (types A-D in figs. 10-13), but never included breaking
the new frame and shifting the attachment outward as in P. vicina (e.g., Fig. 4C).
Instead, the spider usually made a dragline attachment to the new frame, and
then a second attachment to the frame just on the far side of the new radius as it
swung its abdomen in this direction prior to returning to the hub (Fig. 14) (a
similar slight separation of the second attachment in the same direction occurs in
Metazygia sp., Micrathena sp., and Eriophora sp. — Eberhard unpub.). The older
frame segment (dotted lines between attachment points [large dots] in Fig. 14)
often sagged perceptibly when the spider broke the radius and returned to the
hub. Occasionally a spider reinforced or perhaps tightened a frame line by adding
a line attached on either side of the new radius before returning to the hub.

Spiders never modified three or more adjacent radii in orderly sequences, nor
were frames ever built in strict order in adjacent sectors as in P. vicina. Usually it
was not possible to observe if the spider made more than a single attachment at
the hub after laying a radius, but recognizable hub spiral was almost never laid
until radii were complete. One otherwise apparently normal spider seemed to
have difficulty in making attachments, and paused perceptibly each time it
attached; this spider made only a single attachment as it arrived at the hub after
laying most radii; occasionally it made up to three attachments prior to leaving to
build the next radius.

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Figure 10. — Sequence of events in L. mariana frame construction Type A (conventions as in Figs. 3
and 4).

Figure 11. — Sequence of events in L. mariana frame construction Type B (conventions as in Figs. 3

and 4).

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

217

Figure 13. — Sequence of events in L. mariana frame construction Type D (conventions as in Figs. 3
and 4).

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Figure 14. — Details of last attachment in frame construction sequences of L. mariana (e.g., D in
Figs. 12, 13). As the spider breaks the radius (vertical line) it attaches to the frame on both sides of
the original radius-frame attachment, thus allowing a short segment of the frame to go slack
(conventions as in Fig. 3).

Frame construction was intercalated with other activities such as radius
construction, and showed a similar distribution throughout web construction to
that in P. vidua (Fig. 9). Partial replacements of radial lines had the same general
pattern (Fig. 15), but had a stronger tendency to occur later in construction (P <
0.05) comparing webs >30% finished with earlier stages of construction in the
two species). Frames were less likely to be built in succession by L. mariana than
by P, vicina: the behavior immediately preceding frame construction was more
often radius construction, and less often frame construction in L. mariana ( P <
0.01 for both, N = 84 for L. mariana , 68 for E vicina). The most common major
type of frame construction (Figs. 10-13) was A (60% of 93 in study webs),
followed by C (19%), B (15%), and D(5%).

In contrast to P vicina , the choice of exit radius was not consistent. In only
100 of 211 cases was the side chosen the same as that for the previous radius (P
> 0.5). The angles between the last six radii were also larger in L. mariana (Fig.
16, P < 0.01). This was due to the tendency of 1, mariana to lay successive radii
in opposite halves of the web rather than to there being fewer radii in L. mariana
webs; finished L. mariana webs averaged 21.4 + 3.2 radii while those of P. vicina
averaged 18.3 ±4.1. Nearly 60% of the radii in L. mariana webs made angles of
more than 120° with the radii that immediately preceeded them.

Nephila clavipes . — Mesh on either side of the orb was built prior to and during
the first stages of orb construction. No behavior resembling PHR was observed.
The mesh was also frequently extended after part of the sticky spiral was
complete. Mesh construction was very complex, but included some components
of radius and frame construction. It will not be described here.

L Exploration : Exploration behavior included descents on single vertical lines,
occasional long periods of immobility, and “around the comer” substrate
attachments. On four occasions a spider went all the way (360°) around a wire or
a string in making such an attachment. A central area (the future hub) where
lines converged was always established very early in construction, both in webs
built from scratch and those with a mesh already present. Commonly the spider

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

219

Philoponella vicing
Leucauge mariana

,40

LU 20
cr

111

<N CO

FRACTION FINISHED (9a)

3! * *?. ^

f> oo o>

FRACTION FINISHED

Figure 15. — Relative numbers of partial replacements at different stages of orb construction by P
vicina ( N = 72 replacements in 17 webs) and L. mariana (N = 154 replacements in 40 orbs) (state of
construction indicated by fraction of final number of radii already built). Since some observations
began after the first radii had been laid, replacements made in the very earliest stages (<0.20) are
under-represented (inset shows the percentage of the final number of radii already present when
observations began).

Philoponella vicina
Leucauge mariana

LU20

IJL

0-30 31-60 61-90 91-120 121-150 151-180

ANGLE

Figure 16. — Distributions of angles between successive radii for the last five radii laid in 16 P. vicina
and 18 L. mariana webs (partial replacements are not included).

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expanded the web by walking to the edge and then moving sideways along the
substrate before attaching its dragline. Spiders usually slowed appreciably as they
moved from a silk line onto the substrate.

Although spiders usually returned from excursions away from the hub along
the dragline they had laid on the way out, they never performed one of the most
common behaviors of P. vicina and L. mariana : move away from the hub, attach
the dragline, then turn back and break and replace the dragline just laid while
moving back to the hub (e.g., Fig. 3). Spiders were capable of breaking and
reeling the line they were on, but did this only while removing lines which had
not just been laid, and nearly always (40 of 42 times) while moving away from
the hub. Many other lines were broken and then simply released and allowed to
sag free; breaks of this sort often occured while the spider was at the hub (14 of
43 cases). Since lines were seldom shifted or replaced, the site of the hub did not
change as lines were reconnected as sometimes occurred in P vicina and L.
mariana . In one case, however, a second hub developed during mesh construction
and became the hub of the orb while the first “hub” came to be in the mesh on
one side.

Some radii were added early in orb construction without breaking lines: the
spider moved away from the hub on a pre-existing radius and then sideways
along a frame line or the substrate, attaching its dragline and returning along it,
reinforcing it with a second dragline. Other excursions of this sort (6 of 14)
resulted in two new radial lines, as the spider continued sideways after the first
attachment and attached its dragline a second time before returning to the hub
along the line laid on the way out. Neither of the other two species exhibited
these behaviors.

II. Frame and radius construction : Frames were never laid in strict order as in
P. vicina. Hub loop construction did not begin until several radii, a substantial
amount of mesh, and often some of the frames had been laid. Once it
commenced, hub loop construction occurred after each excursion to build radii or
frames.

Frame construction behavior was extremely variable. Types A and B (Figs. 17,
18) were most common (frequencies were 39 and 12% respectively in 101
sequences observed). Twenty-eight additional types of frame construction were
seen, none repeated more than three times. Some alternative behaviors were
closely related to the most common types. For example one (Fig. 19) was the
same as B except for an extra trip across the sector. The points where
attachments were made in both A and B varied substantially. Thus the variant in
Fig. 20 involved the attachment of a second new radius to the end of the first,
and that in Fig. 21 attaching the second new radius beyond the first as the spider
moved along the frame; both of these behaviors were similar to Type A. Other
variants involved laying similar lines but using alternative paths to lay them (Fig.

22) , and breaking and reeling lines instead of simply walking along them (Fig.

23) . Still further variants, however, had little relation to more typical patterns
(Figs. 24, 25).

All types of frame construction involved laying two radial lines in the process
of constructing a single frame, and none involved breaking any of the lines laid
while the frame was being made; in both respects N. clavipes behavior differed
from all types of frame construction seen in P. vicina and L. mariana.

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

221

Figure 17. — Sequence of events in N. davipes frame construction Type A (conventions as in Figs. 3

and 4).

Figure 18. — Sequence ol events in N. davipes frame construction Type B (conventions as in Figs. 3
and 4).

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Figure 19. — Sequence of late events in N. clavipes frame construction. Behavior was similar to that
in Fig. 18 (stages A-C were identical) except the spider made a trip a cross the entire sector (D')
before crossing to lay the second radius and return to the hub (E') (conventions as in Figs. 3 and 4).

Radius construction usually also involved two attachments to the frame and
resulted in two radii being laid during each trip away from the hub (Eberhard
1982, character F2). In 44 of 353 cases, however, I was certain that only a single
attachment was made at the frame, and the second dragline was laid alongside
the first (Eberhard 1982, character F3). Nearly all of these exceptional single radii
were relatively short, and 34 of 44 were above rather than below the hub (P <
0.001 compared with double radii). The spider always left the hub on the

Figure 20. — Sequence of events in N. clavipes frame construction similar to that in Fig. 17 except
the spider attached the second radius right at the point on the frame where the first was attached (C)
(conventions as in Figs. 3 and 4).

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

223

Figure 21 J — Sequence of events in N. ciavipes frame construction similar to that in Fig. 17 except
the spider moved along the new frame past the site of the first new radius before attaching the second
new radius (C) (conventions as in Figs. 3 and 4).

uppermost of the two radii bounding the sector where the radial lines would be
laid (N > 200). In four cases a spider interrupted hub loop construction and
started away from the hub as if to lay radii, but turned back after moving only a
mm or so and resumed hub construction. Similar “false starts” occur in U.
diversus (Eberhard 1972).

Spiders showed individually consistent differences in the pattern of velocities of
movement during radius construction. Some moved inward and outward at more
or less the same, relatively slow rate. Others moved part way out relatively
slowly, then moved very quickly the rest of the way out, along the frame, and
part way in, then slowed again as they approached the hub.

As first described by Kingston (1922) and Wiehle (1931), radius construction
continued after the spider widened the space between the loops it was making at
the hub, thus changing from hub to temporary spiral construction. Most radii
laid during temporary spiral construction were below rather than above the hub
(103 of 1 15 compared with 91 of 238 radii laid earlier, P < 0.001).

Other uloborids. — Hyptiotes cavatus (Hentz) build triangular webs that
probably represent segments of orbs. Previous accounts of construction behavior
(Nielsen 1932; M ai pies and Marples 1937; Eberhard 1982) are not entirely clear
on the early stages of construction. I observed only a single web of H. cavatus
being built, but was able to understand some of what I saw. There was no
behavior corresponding to PHR. The single frame was built after two radii were
in place, and resembled type B pre-PHR behavior in P. vicina in both the
replacement of the exit radius and the shift of the frame attachment outward

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Figure 22. — Sequence of events in N. clavipes frame construction similar to that in Fig. 17 except
the spider turned back after attaching the second new radius (C), using the second of the two exit
radii to make its final return to the hub (conventions as in Figs. 3 and 4).

(Fig. 5). It bore no resemblance to the frame construction behavior reported by
Marples and Marples (1937) for H. paradoxus. The other two radii were then
added without any lines being broken, and without any attachments other than
the initial attachments at the hub and the frame. Temporary spiral construction
began immediately after the fourth radius was laid, without any hub spiral having
been laid. Thus H. cavatus radius and frame construction resemble pre-PHR
behavior in P vincina except for the last two radii; these resembled post PHR
construction except that no hub was made. The descriptions of II. paradoxus

construction by Marples and Marples (1937) agree on all of these points other

than the exception noted above.

Though observations on other genera are still needed, additional observations
of construction of single webs by R tingena , Uloborus trilineatus , and Zosis
geniculatus suggest that several of the special behaviors seen In P. vicina and U.
diversus are widespread in uioborids. All species replaced a proto-hub early in

radius construction, and broke newly laid frames to shift the frame attachment

outward during frame construction (e.g., Fig. 4C). Only after PHR did U.
trilineatus and Z. geniculatus make series of hub attachments during radius
construction. Both P tingena and U. trilineatus modified a series of radii just
before PHR; in U. trilineatus I noted that these radii were in strict sequence as in
P vicina .

Other araneoid orb-weavers. — Prior to beginning this study, I observed frame
construction in 19 tetragnathid and araneid genera ( Nephilengys , Tetragnatha ,

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

225

Figure 23. — Sequence of events in N. clavipes frame construction similar to that in Fig. 17 except
the previous radius on which the spider moved away from the hub was broken and replaced (A)
(conventions as in Figs. 3 and 4).

Chrysometa, Gasteracantha, Micrathena, Pronous, Alpaida, Argiope, Cyclosa,
Cyrtognatha, Enacrosoma, Eriophora, Eustala, Hypopthalma, Larinia,
Metazygia, Parawixia, Neoscona, Verrucosa , Wagneriana , and Witica ), in the
theridiosomatid Epeirotypus sp., and in the mysmenid Mysmena sp. While some
of my notes do not mention how early in web construction my observations
began, very early stages were certainly observed in Nephilengys, Gasteracantha,
Micrathena (three species), Alpaida, Cyclosa, Hypophthalma, Metazygia,
Neoscona, Tetragnatha, Epeirotypus , and Mysmena. In no case did any species
perform any behavior similar to PHR; since I had observed PHR in U. diversus
before I made these observations, I am confident that I would have noted
anything similar to PHR if it had occurred.

At the conclusion of the study I observed the construction of webs by a
different Metazygia sp. and Acacesia hamata , and again failed to note any
behavior remotely similar to PHR.

DISCUSSION

A. Distinguishing characters and their homologies. — In order to compare the
behaviors of different groups, it is necessary to first decide which behaviors differ,
and which differences or similarities are homologous. Unfortunately, these
descriminations are influenced by what seem to be unavoidably subjective
decisions. Analysis at a fine level (e.g., movements of given legs) can give

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Figure 24. — Sequence of events in complex N. clavipes frame construction behavior (conventions as
ijn Figs. 3 and 4).

different results from that at higher levels of organization (e.g., inclusion of the
context in which the movement is performed). For instance, I have previously
interpreted the tapping behavior of legs I to the side during sticky spiral
construction to locate previously laid lines as a possible synapomorphy of
Araneidae (Eberhard 1982). But undoubtedly many other orbweavers, and indeed
other spiders which do not make orbs occasionally tap their front legs laterally to
locate lines (or other objects). So if tapping to the side is itself the unit being
compared, the behavior is not a synapomorphy.

The problem, of context is acute in behavior since a common and important
pattern in behavioral evolution is that of changes in context; a given movement
or sequence of movements is transposed from one context to another. This
pattern of evolution implies that the standard cladistic techniques of weighting
characters equally is inappropriate, since (all other things being equal)
convergence via such transpositions is more likely to evolve than is convergence
via independent invention or reinvention; transpositions should thus be given less
weight in constructing phytogenies.

How great must a change in context be for a homology to be rejected? How
can the “size” of a change in context even be measured? These questions seem not
to have straight-forward answers. In the example of tapping behavior it seems
relatively clear that including the context of the leg movement as a part of the
character is reasonable. In other cases, however, this decision is more difficult.
Take for example the proto-hub removal behavior of uloborids described in this
study. Many araneoid spiders remove the central area of their hubs near the end
of orb construction (e.g., Eberhard 1982, 1987c; Coddington 1986a). Is this

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

227

Figure 25. — Sequence of events in complex N. clavipes frame construction behavior (conventions as
in Figs. 3 and 4).

removal behavior homologous with the PHR of uloborids, but simply displaced
to a later position in the sequence of construction? Or is it an independently
derived process which has converged on PHR in general form?

Similar problems occur in simple descriptions. Is the behavior in Fig. 11A-B,
where L. mariana stopped and attached to a line before reaching the substrate
different from that in Fig. 13B, where the spider moved past the end of a silk line
and laterally (the only direction possible on the wire hoop) before attaching?
These problems are related to a general problem plaguing taxonomy — that of
deciding how to code characters (behavioral or otherwise), and of the lack of
information correlating the amount of phenotypic difference with the degree of
improbability that a given phenotype could be derived independently.

As I have no certain answers to these types of questions, the practice adopted
in both the descriptions above and the discussion below is conservative: claims of
homology are minimized, and differences are thus emphasized. This focus stems
both from a reaction against previous oversimplified accounts of construction
behavior, and from one of the basic objectives of this study: to provide additional
characters to help in the resolution of the controversy surrounding the phylogeny
of orb weavers (the final answer to which obviously must depend on as many
characters, behavioral and otherwise, as possible). Future workers may decide,

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one would hope with better criteria and/or evidence than those which are
presently available, that some distinctions made here are unjustified, and combine
categories. The opposite process, splitting two categories from a single one in
which differences had not been reported, would not be possible.

B. Comparisons between species. — One consistent difference between frame
construction by P. vicina and that of the araneids L. mariana and N. clavipes was
that all frame lines constructed by the uloborid were broken as the spider
returned to the first radius laid, and were then shifted outward along this radius
(Figs. 4-8). This behavior never occurred in L. mariana or N. clavipes. These
observations agree with Coddington’s (1986a) observations of one genus of
uloborid and 17 genera of orb-weaving araneoids, and reinforce his idea that this
difference may distinguish uloborids and araneoids.

A second difference was that P. vicina usually chose exit radii that were on the
leading edges of sectors to be filled during both frame and radius construction,
while L. mariana showed no preference. The same preference was shown by U.
trilineatus and by U. diversus (at least during frame construction — Eberhard
1972). The difference with L. mariana may be partly related to the fact that the
uloborids make hub spiral between all or nearly all radii laid after PHR, and are
thus turning in an orderly manner at the hub, while L. mariana generally makes
no hub spiral until all radii are in place. In non-horizontal webs, both L. mariana
(Eberhard unpub.) and N. clavipes generally exit on the upper of the two radii
bounding the sector where the radius or frame is to be laid, just as usually occurs
in araneids such as A. diadematus Cl. (Reed 1968), Micrathena plana (Koch),
Verrucosa sp., and Cyclosa caroli (Hentz) (Eberhard unpub.).

The most dramatic differences between the behavior of P. vicina and the
araneoids are associated with PHR. PHR always occurred in undisturbed P.
vicina , but never occurred in L. mariana or N. clavipes. In addition, PHR in P.
vicina was always preceeded by a strictly ordered sequence of frame construction
and radial modifications on adjacent radii, while the order of operations in the
early stages of L. mariana and N. clavipes webs did not follow strict sequences
involving adjacent radii. Examination of literature accounts of uloborid and
araneoid behavior plus the brief observations of other uloborids and araneoids
reported here suggest that both PHR and strict ordering of frames probably
distinguish uloborids from araneoids. No araneoid has ever been reported to
perform any behavior during the early stages of orb construction that might
correpond to PHR (see detailed observations of Hingston 1922; Tilquin 1942;
Koenig 1951; Mayer 1952; Witt et al. 1968 as well as the observations reported
here). The most similar behavior is the possibly non-homologous hub replacement
(see above) performed by some theridiosomatids and anapids after the web is
otherwise complete (Eberhard 1982, 1987c; Coddington 1986a). On the other
hand, all species of orb weaving uloborids that have been observed (two
Uloborus , two Philoponella , and one Zosis) show clear PHR.

The few accounts of sequences of frame lines in araneids (Tilquin 1942 on
Araneus sp. and Argiope; Mayer 1952 on Araneus diadematus ; Dugdale 1969 on
Micrathena gracilis ), do not show a strict sequence of frames in adjacent sectors
of the orb, and Tilquin (1942) states that sequences of frames vary and that
radius construction often interrupts frame construction (p. 208 ff.). The only two
uloborid orb weavers carefully checked in this study, U. trilineatus and P. vicina ,
both modify adjacent radii in strict order immediately preceeding PHR, often

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

229

making a series of adjacent frame lines. U. diversus also often makes series of
adjacent frames (Eberhard 1972). Thus, as far as these incomplete data go,
orderliness in frame construction also distinguishes uloborids from araneoids.

Angles between successive radii were larger in L. mariana than in P vicina and
the same difference apparently occurs when the araneid M. gracilis is compared
with the uloborid U. diversus (Eberhard 1972). Apparently araneids often tend to
lay successive radii on nearly opposite sides of the web (Kingston 1920; Witt et
ah 1968; Uetz 1986). This difference is probably related to the fact that uloborids
lay hub spiral during radius construction while most araneoids lay less or none.
Radii on opposite sides may be advantageous in balancing tensions at the hub,
but such adjustments would probably not be practical for a spider which is also
laying hub spiral, since an excessive number of hub loops would be necessary to
allow completion of radius construction, especially in view of the relatively high
numbers of radii in some uloborid orbs (Eberhard 1986).

Another possible difference was that P. vicina used legs IV to reel in slack silk
during frame construction while the others did not. Both L. mariana and N.
clavipes tightened slack frame lines using a different behavior involving the front
rather than rear legs. (L. mariana was never seen to reel in any line with a leg IV
in any context, but Nephila sometimes ascends its dragline backwards after
attacking prey — Robinson and Robinson 1973). Other uloborids ( Hyptiotes —
Marples and Marples 1937, and Opell 1985; Miagrammopes — Lubin et al. 1978)
reel in lines with legs IV.

Observations of a slow-moving L. mariana as it laid radii revealed that the
spider usually failed to lay hub lines between successive radii. Hub lines were also
not laid during the early stages of radius construction by N. clavipes. These
observations are not in accord with Coddington’s statement (1986a: 344) that
both “araneoids and uloborids construct frames and radii as a subroutine within
hub construction.” Since it is often very difficult to determine how many hub
attachments are made between successive radii (I was generally unable to decide,
for example, whether multiple attachments were made by P. vicina before PHR),
Coddington’s claim should be treated with caution.

Changes in the types of radius and frame construction behavior before and
after PHR which are similar to those of P vicina appear to occur in U.
trilineatus, Z. geniculatus, and P. tingena. Similar changes in frame (but not
radius) construction occurred as web construction in L. mariana progressed. In
all cases there was a gradual reduction in the removal of lines already in place in
the web.

The order and kinds of lines laid during frame construction behavior was
clearly variable in each of the three species studied in detail here. Both P. vicina
and L. mariana had several common patterns, and additional rare variations.
Probably a few further variants remain to be described, perhaps including some
of the sequences I saw but failed to understand (see Methods). The behavior of
N. clavipes was much more variable, and the total number of variations may be
quite high (>507). Some literature descriptions of other species’ behavior may
represent still further variations (see Tilquin 1942 and Reed 1968 on Araneus ;
Marples and Marples 1937 on Hyptiotes). This variability contrasts with the
stereotypy seen in later stages of orb construction (Tilquin 1942; Eberhard 1982).
As has been noted before (Witt et al. 1968; Eberhard 1972), an orb weaver
gradually isolates itself from its surroundings and from the need to respond to

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them as it builds, and it is perhaps not surprising that building behavior in later
stages is more stereotyped.

Some shifts in P. vicina behavior before and after PHR are not entirely
consistent, and may represent imprecision in its behavior (Eberhard in press). For
example, behavior typical of pic- PHR such as short partial replacements
occasionally appeared just after PHR (6 of 130 replacements in the study webs).
Such mixing was especially pronounced when spiders built after their first radii
and frames of the morning had been destroyed.

C. Implications regarding the evolutionary origin(s) of orbs. — Several lines of
evidence from this paper suggest that the transitions in building behavior
postulated by the rnonophyletic and polyphyletic theories of the origin of orb
webs differ less than has been previously appreciated. Coddington (1986a) noted
that the similarity between uloborid and araneoid frame construction behavior
argues for a rnonophyletic origin of orbs, since other “perfectly feasible
alternatives” exist and are actually described in mistaken accounts in the
literature. I agree that these published accounts are probably mistaken, but not
that they are so obviously feasible for spiders. There are two kinds of mistakes.
In one (Comstock 1940; Levi and Levi 1968; Levi 1978) the spider is described as
establishing a frame line by running along the substrate from one anchor to
another. This is probably usually physically impossible in nature, where webs are
often attached to objects which are too separated for the spider to walk directly
between them, (e.g., many leaves, twigs), and this behavior did not occur even in
the wire frames of this study. The other type of error (McCook 1889; Kingston
1920; Dugdale 1969) describes the frames as being laid before any radii are built.
But from very early in the exploratory phase of both uloborids and araneoids
there are intersections between lines at central points within the area where the
orb will be built, and the spider's activities seem organized around these points as
it moves out from them toward the edge of the web, then returns (see Tilquin
1942; Koenig 1951; Mayer 1952; LeGuelt 1966; and Eberhard 1972 as well as this
study). In fact, this general radial type of pattern of spinning also occurs in other
spiders that do not build orbs, and may be very ancient in spiders (Eberhard
1987d). In sum, the possibility that very ancient, pre-orb traits plus “fabricational
constraints” (Coddington 1986a) explain the similarity between uloborid and
araneoid frame construction rather than more recent common ancestry of the two
groups is more likely than suggested by Coddington (1986a).

Two related points deserve mention. Feasible alternatives for radius and frame
construction do exist which neither uloborids nor araneoids are known to
employ. These involve the spider not retracing the line it has just laid as it returns
to the hub (e.g., Fig. 26). Thus the spider’s tendency to turn and retrace its steps
hubward along the same radial line it has just laid, in preference to using other
nearby lines is a character shared by uloborids and orb-weaving araneoids.
Whether this character is primitive or derived with respect to that of possible
sister groups is not certain. The fact that Filistata returns “hubward” (toward its
retreat) along the more or less radial line It has just laid while spinning sticky silk
(Eberhard 1987d) suggests this may be a primitive trait.

A second point is that the variation In frame construction behavior
documented here makes comparisons between uloborids and araneoids more
difficult to interpret. For Instance, Coddington (1986a) notes that araneoid and
uloborid frame construction behavior is “strikingly similar”, noting with reference

EBERHARD— EARLY STAGES OF ORB CONSTRUCTION

231

Figure 26. — A simple, feasible frame construction sequence which is apparently never used by orb
weavers, in which the spider fails to return to the hub along a newly laid radial line (B).

to U. diver sus and A. diadematus that “both construct a radius each time they
construct a frame line.” As shown here, this statement is incorrect for both P
vicina (Fig. 5) and L. mariana (Fig. 11). Some variants of frame construction are
similar in the two species (Figs. 4 and 10, 5, and 11, 8 and 12), while others may
be unique to one or the other (Figs. 6, 7, 13). It is difficult to decide how great
the degree of difference between two behaviors should be to merit recognizing
them as being different (see discussion above).

The behavior of N. clavipes is probably primitive with respect to that of P.
vicina and L. mariana in at least two respects. The great variability in frame
construction is probably primitive, since it seems likely that the evolution of orb
construction involved a rigidification, or weeding out of much greater variability
in ordering and locations of lines seen in non-orb weavers (Szlep 1965; Robinson
and Lubin 1979) (see Eberhard in press). In addition, N. clavipes did not break
and reel lines during the stages of construction in which deinopids (Coddington
1986b), and uloborids and araneoids do so (this study). This lack of breaking and
reeling behavior (which appears to be absent in Nephilengys also — unpub.) may
also be primitive, since secondary loss would probably be disadvantageous.
Breaking and reeling allows the spider to adjust tensions in the web as it is built
(Eberhard 1981), to shift the site of the hub as exploration progresses, to
eliminate stray lines laid early in the process that are not appropriate for the final
web, and to quickly recycle the material from unwanted lines (Peakall 1971;
Tillinghast and Townley in press). These functional considerations imply that
shifting and replacing lines would be especially important early in orb
construction, an interpretation which is supported by the fact that this is when
uloborids perform these behaviors.

In addition, the few descriptions of the building behavior of possible outgroups
such as theridiids (Szlep 1965; Eberhard unpub. on Chrosiothes sp.), pholcids

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(Eberhard and Briceno 1985; Briceno 1985) and a diguetid (Eberhard unpub. on
Diguetia canities ) do not include breaking and reeling, suggesting that breaking
and reeling may be a derived behavior. The theridiid Synotaxus does break and
replace dry lines, but the behavior occurs while the spider is producing sticky
lines (Eberhard 1977), and may not be homologous with breaking and reeling
during frame construction. Clearly, additional data from possible sister groups
are badly needed.

If Nephila's highly variable construction behavior and its lack of breaking and
reeling in radius and frame construction are both primitive, then the
circumstances under which the argument for a monophyletic origin of orbs can be
true are limited in such a way that differences between the character state
transitions in the mono- and polyphyletic hypotheses are reduced. This conclusion
is based on the following considerations. Nephila shows several synapomorphies
with other orb weaving araneoids (aggregate glands, flagelliform glands, serrate
hairs, paracymbium on male palp, inner leg IV pushes sticky silk when attach —
Coddington 1986a), and so is likely to be more closely related to these spiders
than to uloborids or deinopids. The argument that all orb weavers are descended
from a single cribellate orb-weaving ancestor thus has two possible forms with
respect to breaking and reeling: either the common ancestor used breaking and
reeling behavior and Nephila has secondarily lost this ability; or the ancestor
lacked this character, and it was acquired independently in both uloborids and
other araneoids. Similarly, either the ancestor lacked relatively invariable frame
construction, or Nephila secondarily lost it.

Since secondary loss is unlikely on functional grounds, at least in the case of
breaking and reeling (above), the more likely monophyletic account is that the
ancestor lacked this behavior. This in turn would imply that if orbs are
monophyletic, breaking and reeling was acquired independently by both uloborids
and non-nephiline araneoids. In each line the behavior would then have
revolutionized orb construction, being incorporated into exploration, radius and
frame construction, and perhaps in hub removal in somewhat different ways.

This evolutionary sequence is relatively similar to the alternative, polyphyletic
hypothesis in having major parts of orb construction evolving convergently. In
sum, the observations here imply that even if all orb weavers are descended from
an orb-weaving ancestor (more data are needed on this point — Shear 1986), some
major aspects of orb construction behavior appear to have arisen independently
in different evolutionary lines.

ACKNOWLEDGMENTS

I thank F. A. Coyle for hospitality; B. D. Opell, J. A. Coddington, and
especially H. W. Levi for invaluable aid identifying spiders; W. A. Shear, J. A.
Coddington and B. D. Opell for criticisms of previous drafts; and G. Hills for
help preparing the manuscript. The Vicerrectoria de Investigacion of the
Universidad de Costa Rica provided financial support.

LITERATURE CITED

Briceno, R.D. 1985. Sticky balls in webs of the spider Modisimus sp. (Araneae, Pholcidae). J.

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Coddington, J. A. 1986a. The monophyletic origin of the orb web. Pp. 319-363, In Spiders, Webs,
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Dugdale, B. E. 1969. The weaving of an engineering masterpiece, a spider’s orb web, done at Fryson
Lakes, N.J., August 8, 1942, as observed by B. E. Dugdale, structural engineer. Nat. Hist.,
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Eberhard, W. G. 1972. The web of Uloboms diversus (Araneae: Uloboridae). J. Zool, London,
166:417-465.

Eberhard, W, G. 1977. ‘Rectangular orb’ webs of Synotaxus (Araneae: Theridiidae). J. Nat. Hist.,
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Eberhard, W. G. 1981. Construction behavior and the distribution of tensions in orb webs. Bull.
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Eberhard, W. G. 1987b. How spiders initiate airborne lines. J. Arachnol., 15:1-9.

Eberhard, W. G. 1987c. Web-building behavior of anapid, symphytognatfaid and mysmenid spiders
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Eberhard, W. G. 1987d. Construction behavior of non-orb weaving cribellate spiders and the
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Eberhard, W.G. (in press). Imprecision in the behavior of Leptomorphus sp. (DIptera,
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Eberhard, W. G. and R. D. Briceno. 1985. Behavior and ecology of four species of Modisimus and
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Forster, R. and L. Forster. 1973. New Zealand Spiders an Introduction. Collins, London.

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Manuscript received November 1988, revised February 1990.

1990. The Journal of Arachnology 18:235

RESEARCH NOTES

DISCOVERY OF CAVIPHANTES SAXETORUM
IN NORTH AMERICA; STATUS OF
SCIRONIS TARSALIS (ARANEIDA, LINYPHIIDAE)

The genus Caviphantes Oi, 1960 was reviewed by Wunderlich (1979), who
placed in synonymy the somewhat better-known name Lessertiella Dumitrescu
and Miller, 1962; that synonymy is now generally accepted. The genus contains
four species: Caviphantes samensis Oi from Japan, Caviphantes dobrogicus
(Dumitrescu and Miller) from Rumania and southwestern U.S.S.R., Caviphantes
pseudosaxetorum Wunderlich from Nepal, and Caviphantes saxetorum (Hull)
from Britain and Germany. The first two occur in caves, soil, and litter; the third
in litter; the fourth under stones in dry beds and sandy banks of rivers.

In Europe, C. saxetorum is rare as well as habitat-limited (Cooke and Merrett
1967; Roberts 1987); its discovery in Oregon, U.S.A., is therefore remarkable.
The specimen, a male at the Thomas Burke Memorial Washington State
Museum, University of Washington (UWBM), does not differ significantly from
the best available description (Cooke and Merrett 1967). I am forced, therefore,
to consider it a member of this species despite the geographic separation. The
collection data are as follows:

OREGON: Lane Co.: Lookout Creek (564 m), 44.223°N 122.228°W, 13 April-4
May 1983 (pitfalls), G. Parsons leg. The site is in the H. J. Andrews
Experimental Forest. The macrohabitat is a serai forest of 40-year-old Tsuga
heterophylla (western hemlock), with understory of ferns, Polystichum munitum,
and the herb Oxalis oregona. Due to its collection by pitfall, the microhabitat of
the specimen is unknown; the site is 375 m from the boulder-strewn bed of
Lookout Creek but only a short distance from an intermittent tributary, so the
habitat may be the same as in Britain.

I think it highly unlikely that this collection represents an introduced
population. In Europe the species is far from synanthropic, and the Oregon
locality is remote (11.5 km from the nearest small town; 70+ km from Eugene, the
nearest commercial center). If C. saxetorum is, as I suspect, a truly Holarctic
species, it would be expected, and should be searched for, in other North
American and Eurasian localities.

The tracheal system of Caviphantes is linyphiine, not erigonine (Millidge 1984).
Millidge placed the genus in his “ Stemonyphantes group,” an informal
assemblage of linyphiine spiders with “primitive” (i.e., simple) female genitalia. I
feel that Caviphantes and its near relatives fit fairly well in Millidge’s formal
subfamily Linyphiinae, having in common an epigynal atrium formed between the
dorsal and ventral plates which contains the genital openings (see Millidge 1984:
fig. 17). The only difference from “typical” Linyphiinae is that the dorsal plate is
not extended in a scape. Caviphantes shares major genitalic features, the

1990. The Journal of Arachnology 18:236

epigynum as described above and complex palp with long, looped embolus
originating centrally, with its nearest relatives, the European Mioxena and the
American Scironis (for details of palpal conformation see Millidge 1977; Cooke
and Merrett 1967). Mioxena has the simplest palp of the three, Caviphantes the
most complex. These three genera have identical chaetotaxy: tibial spines 2-2-1-1,
Tml = 0.3 0.45, TmlV absent.

The genus Scironis Bishop and Crosby, 1938 has hitherto been considered
erigoeme. I have done a tracheal determination on a male Scironis tarsalis
(Emerton) from Alaska (UWBM) and found a linyphiine-type tracheal system
(Millidge 1984: fig. 130). The epigynum (females, UWBM, from Washington and
Alaska) is very similar to that of C. saxetorum , but the palp (Bishop and Crosby
1938: fig. 35) is sufficiently distinct to maintain Scironis as a genus, which as far
as known is monotypic. Scironis autor Chamberlin has been transferred to
Scoiinotylus, and Scironis sima Chamberlin also belongs elsewhere. The Scironis
palpal conformation superficially resembles that of the erigonine Pocadicnemis ,
but the tracheal systems preclude close relationship.

I thank James Mclver of Oregon State University for the gift of the C
saxetorum specimen and information on its habitat.

LITERATURE CITED

Bishop, S. C. and C. R. Crosby. 1938. Studies in American spiders: Miscellaneous genera of
Erigoneae, part IL J. New York Entomol. Soc., 46(1): 55- 107.

Cooke, J. A. L. and P. Merrett. 1967. The rediscovery of Lessertiello saxetorum in Britain (Araneae:

Linyphiidae). J. Zool. (London), 15 1(3): 323 328, plate 1.

Millidge, A. F. 1977. The conformation of the male palpal organs of Linyphiid spiders, and its
application to the taxonomic and phylogenetic analysis of the family (Araneae: Linyphiidae). Bull,
British Arachnol. Soc., 4(1): 1-60.

Millidge, A. F. 1984. The taxonomy of the Linyphiidae, based chiefly on the epigynal and tracheal
characters (Araneae: Linyphiidae). Bull. British Arachnol. Soc., 6(6): 229-267.

Roberts, M. J. 1987. The Spiders of Great Britain and Ireland. Vol. 2. E. J. Brill, Leiden. 204 pp.
Wunderlich, J. 1979. Linyphiidae aus Nepal, III. Die Gattungen Caviphantes Oi 1960 und Lessertielia
Dumitrescu & Miller 1962. Senckenbergiana Biol., 60(1 /2):85-89.

Rodney L. Crawford, Thomas Burke Memorial Washington State Museum,
University of Washington, Seattle, Washington 98195 USA.

Manuscript received , accepted October 1989.

1990. The Journal of Arachnology 18:237

ENTOMOPHAGOUS FUNGI AS MORTALITY AGENTS
OF BALLOONING SPIDERLINGS

Organisms with high fecundity are expected to have a high incidence of juvenile
mortality. Many species of spiders produce a hundred or more eggs per egg sac
and multiple broods per year. Juvenile spiders are subject to the usual array of
parasites and predators, but thee those spiderlings that balloon for dispersal are
confronted with many additional mortality factors. Those that have been cited in
the literature are predation, landing in an inhospitable site, and harsh weather
conditions.

I propose that an additional and significant mortality factor affecting
ballooning spiders is infection by entomophagous fungi. Several investigators
have reported on adult spider mortality by fungi in the field and in the
laboratory. In Panama, Nomuraea sp. was found on five species of the Araneidae
(Nentwig 1985). Humber and Rombach (1987) found the fungus Torrubiella
ratticaudata its anamorph Gibell.ua davulifera var alba , as well as G. pulchra and
Nomuraea atypicola on salticid spiders. In a recent laboratory study, Greenstone
et al. (1987) demonstrated that spiders across a broad taxonomic range are
susceptible to the fungus, N. atypicola . Here I present evidence of fungal attacks
on juvenile spiders found in a southern deciduous forest.

I collected ballooning spiders from a 45 m forest-meteorology tower in Oak
Ridge, TN from Sept-Oct, 1987 and May- June, 1988. Spiders were collected on
traps made of polyvinyl chloride sewage pipe (outside diameter — 15 cm, length —
94 cm) coated with a fruit tree banding compound (Pest Glue, R. Seabright
Industries). I removed spiders with forceps from the traps daily, soaked the
spiders in paint thinner to remove the sticky material, and then preserved the
spiders in 70% ethanol I identified the spiders to family with the aid of a Wild
dissecting microscope and noted the presence or absence of fungi. Similarly,
insects collected on the traps were also examined for the presence of fungi;
however no fungal growths were ever seen on insects. Traps were cleaned weekly
to ensure that fungi did not grow on the traps, and daily collections of spiders
ensured that infection of individuals occurred prior to entrapment.

In the fall study, 98% (n = 617) of all trapped spiders were immatures that
ranged in size from 1-3 mm. Of these, 20% were infected with fungi that appeared
as a round mass of byphae between leg #1 and leg #2 at the juncture of the coxa
and the eephalothorax. All of the infected spiders were immature Thomisidae.
Fewer infected spiderlings were observed in the spring (5% of total sample, n =
318); however, individuals that represented the families Araneidae, Linyphiidae,
Saitiad ae, Erigonidae, and Thomisidae were infected with fungi. Samples of
infected spiderlings were sent to Richard Humber, Boyce Thompson Institute, for
identification. Due to the absence of sporulative structures, he was unable to
positively identify the fungus; however, based on growth patterns he felt that this
fungus was probably a species of Gibbellula or Torrubiella , some of the most
common and widely distributed spider pathogens.

It would be interesting to know if spiderlings are exposed to fungal spores in
the egg case, as spiderlings before dispersing, or in air as they are ballooning.

1990. The Journal of Arachnology 18:238

This could easily be tested by collecting and culturing spiderlings at various stages
utilizing the techniques described by Greenstone et al (1987).

The observations reported here imply that pathogenic fungi may be important
sources of mortality among spiderlings. Furthermore, infected ballooning
spiderlings may play a role in dispersal of pathogenic fungi.

I would like to thank R. Humber for examining the infected specimens, W.
Herndon for use of his microscope, and S. Riechert, M. Greenstone, and D.
Jennings for comments on the text.

LITERATURE CITED

Nentwig, W. 1985. Parasitic fungi as a mortality factor of spiders. J. Arachnol., 13:272-274.

Humber, R. A. and M. C. Rombach. 1987. Torrubiella ratticaudata sp. nov. (Pyreeomycetes:

Clavicipitales) and other fungi from spiders on the Solomon Islands. Mycologia, 79(3):375~382.
Greenstone, M. H , C. M. Ignoffo and R. A. Samson. 1987. Susceptibility of spider species to the
fungus Nomuraea atypicoia. J. Arachnol. 15:266-268.

Leslie Bishop, Graduate Program in Ecology, The University of Tennessee,
Knoxville, Tennessee 37916 USA.

Manuscript received June 1989, revised November 1989.

THE EFFECT OF HYPTIOTES CAVATUS (ULOBORIDAE)
WEB-MANIPULATION ON THE DIMENSIONS AND
STICKINESS OF CRIBELLAR SILK PUFFS

After constructing their vertical triangle-webs, Hyptiotes cavaius (Hentz) tense
them by reeling in monitoring line thread and holding it between their second and
third legs. When a prey strikes its web, a spider releases this slack silk, suddenly
reducing web tension and causing the web to shake (Lubin 1986; Opell 1982).
This behavior may also change the properties of the web’s cribellar capture
threads that extend across its four diverging “radii.” Like the cribellar threads of
other uloborids, those of H. cavatus are composed of torus shaped puffs of fine
cribellar fibrils deposited around supporting axial fibers (Fig. 1; Opell 1989a).
The reduction of web tension that occurs when spiders respond to prey may
increase the width of these cribellar puffs, thereby exposing more surface area per
unit length of cribellar thread and increasing its ability to hold prey. To
determine if this occurs, we measured the properties of taut and slack cribellar
threads of H. cavatus.

Sixteen adult females were housed individually in frames. From the first web
each spider constructed, we collected a taut cribellar thread sample on a
microscope slide with five raised adhesive supports spaces at 4 mm intervals
(Opell 1989b). From the second web it spun, we collected a slack silk sample by
prodding the spider with a brush and pressing the microscope slide against the
web the instant the spider released its slack silk.

1990. The Journal of Arachnology 18:239

Figure 1. — Scanning electron micrograph of cribellar silk spun by an adult female Hyptiotes
cavatus .

In two of the 32 web samples taken the cribellar silk puff dimensions of only
three of a sampler’s four sectors could be measured. In five of the samples the
stickiness of cribellar silk in only three of the four sectors could be measured. We
measured the width (perpendicular to the thread’s long axis) of one puff and the
length of a series of ten puffs of the cribellar thread in each sector of a sampler at
125X under a compound microscope equipped with Nomarski optics. The mean
values of a thread’s dimensions were used for comparisons. Using techniques
described by Opell (1989b), we measured the force required to pull a 2.30 mm
wide aluminum contact plate free from the cribellar thread in each sector of a
sampler. Before each measurement was taken, this plate was gently rubbed with a
tissue wetted with acetone and was initially pressed against the thread in each
thread sector with a force of 3.03 x 10"5 Newtons. The mean value of a sample’s
sectors, expressed as the force per mm of contact required to pull the plate free of
the cribellar thread, is used for comparisons.

Table 1 summarizes the results of this study. 7-tests show no significant
difference between the mean puff width, puff length, or stickiness (P = 0.90, 0.43,
and 0.28, respectively) of cribellar thread samples taken from taut and slack webs.

Table 1. — Dimensions and stickiness of taut and slack cribellar threads from Hyptiotes cavatus
webs. In each case, sample size is 16.

Variable

Mean

Range

Puff length jum:

Taut

53403

Slack

56416

Puff width jum:

Taut

190

158-220

Slack

189

168-232

Stickiness in Newtons x
Taut

1 0 per mm width of contact plate:

4.30

1.71-9.02

2.09

Slack

3.58

1.00-6.65

1.54

1990. The Journal of Arachnology 18:240

This study shows that changes in H . cavaius web tension resulting from web
maniuplation during prey capture do not serve to alter the measured physical or
functional properties of the web’s cribellar threads. The failure of a spider’s
behavior to change the dimensions of cribellar thread puffs may occur either
because the tensing force exerted on the web’s radial elements is too acute to the
cribellar threads to initially deform them or because the axial fibers of the
cribellar threads resist this elongating force.

However, web-manipulation may yet increase a web’s ability to retain prey.
Unlike the aluminum plate used in this study, the surfaces of insects are beset
with setae that can penetrate the fibril cloud of cribellar threads. By comparing
the stickiness of cribellar threads before and after their tensions were altered, this
study does not fully evaluate the effect of web-manipulation on a thread’s ability
to retain prey that remain in contact with it during these changes. By shaking a
web and altering its tension, web-manipulation may enhance prey retention by
permitting the cribellar thread’s looped surface fibrils to better entwine a prey’s
setae, by causing a struggling prey to contact more cribellar threads, or by more
forcefully pressing cribellar thread against the surface of a prey.

This study was conceived during a discussion with C. Craig and improved by
comments from E. Tillinghast and F. Vollrath. It was supported in part by N.S.F.
grant BSR-8407979 and by a small projects grant from Virginia Polytechnic
Institute and State University’s College of Arts and Sciences.

LITERATURE CITED

Lubin, V D. 1986. Web building and prey capture in Uloboridae. Pp. 132-171, In Spiders: Webs,
Behavior, and Evolution. (W. A. Shear, ed.)5 Stanford Univ. Press, Stanford.

Opell, B. D. 1982. Post-hatching development and web production of Hyptiotes cavaius (Hentz)
(Araneae: Uloboridae). J. ArachnoL, 10:185-191.

Opell, B. D. 1989a. Measuring the stickiness of spider prey capture threads. J. ArachnoL, 17:112-114.
Opell, B. D. 1989b. Functional associations between the cri helium spinning plate and capture threads
of Miagrammopes animotus (Araneida, Uloboridae). Zoomorphology, 108:263-267.

Brent D. Opell, Gabrlelle Moth* and Paula E. Cushing; Department of
Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
24061 USA.

* Present address: 13146 Maltese Lane, Fairfax, Virginia 22033.

Manuscript received October 1989 , revised December 1989.

1990. The Journal of Arachnology 18:241

RESPONSES BY SCORPIONS TO
FIRE-INITIATED SUCCESSION
IN ARID AUSTRALIAN SPINIFEX GRASSLANDS

Scorpions are successful inhabitants of arid and semi-arid grasslands, where
they may reach densities of 5000/ ha and biomasses of 5-20 kg/ ha (Polis et al
1986). Such grasslands are usually burnt frequently, either by lightning-initiated
fires or by Aboriginal people, and yet the responses of scorpions to fire and the
subsequent changes in vegetation are unknown. Indeed, in their review of the
responses of grassland arthropods to burning, Warren et al. (1987) did not cite
any studies of scorpions. In this note, we examine the relative abundance of
scorpions in different vegetation states following fire in spinifex grasslands of arid
central Australia.

Work was conducted at eight sites in the Tanami Desert, Northern Territory,
within 50 km of The Granites (20 32' S, 130 24'E) and 500 km northwest of Alice
Springs. Three samples were taken: from 4 April to 2 May 1985; from 18 October
to 14 November 1985; and 25 March to 22 April 1986. There was little rainfall
during this period, and vegetation declined slightly in cover. Each site was on flat
sandplain dominated by feathertop spinifex, Plectrachne schinzii , but vegetation
varied markedly because of successional change following fire. Two sites each
were in areas burnt in the summers of 1983-84 (state 1, burnt about one year
prior to the beginning of the study), 1982-83 (state 2), 1979-80 (state 5), and 1976-
77 (state 8). Cover of spinifex measured by wheel-pointing (see Griffin 1989a)
averaged 6%, 15%, 37% and 39% in states 1, 2, 5, and 8 respectively during the
three sampling periods discussed in this paper. Cover of other forbs and grasses
averaged 10%, 8%, 1%, and 1% at those times; the principal species were
Leptosema chambersii, Scaevola parvifolia, Rulingia loxophylla, Eragrostis
setifolia , and Aristida holathera. Mean cover of shrubs increased from 1% to 8%
from states 1 to 8; the dominant shrub species was Acacia coriacea. The
vegetational changes caused by fire on these sites (i.e., a flush of forbs and grasses
followed by regeneration of the spinifex and shrubs) were very similar to those
described for R schinzii from a broader region by Griffin (1989b). In this part of
the arid zone, P schinzii dominates the ground layer within about five years of a
fire and is usually burnt again within 10 years.

Scorpions were captured in pit-traps set for small vertebrate animals. Traps
were opened at only one site at any one time, but the order in which the sites
were visited was varied in each sample to minimize the chances of systematic
error due to changing temperatures over the month-long sampling periods. The
traps operated for three days and were set 5 m apart in groups of 10. In the first
sample, three groups of pit-traps were spaced about 200 m apart along a transect,
but four groups were employed in the second and third samples; thus, the number
of pit-trap days was 90 in the first sample but 120 in the other two. A mixture of
plastic buckets 15 cm and 29 cm in diameter was used; details are given by
Morton et al. (1988). Scorpions were removed from the traps each morning and
then preserved in alcohol.

Five species of scorpions were present, but four — Lychas variatus (Thorell)
and Isometroides vescus (Karsch) (Buthidae), and Urodacus armatus Pocock and

1990. The Journal of Arachnology 18:242

Table 1. — Numbers of Lychas alexandrinus captured in pit traps, and sex ratios of adults, in four
different successional states following fire. State 1 was burnt in 1983/84 (1 year since fire), state 2 in
1982/83 (2 years), state 5 in 1979/80 (5 years), and state 8 in 1976/77 (8 years). There were two
replicates for each state. Thirty traps were used at each site for the first sample, but 40 for the final
two samples; in sample 1, numbers in brackets show the scaled-up data used in subsequent analysis of
variance.

Vegetation state

Numbers

Sample 1

12(15)

26(35)

23(31)

13(17)

Sample 2

Sample 3

Total

148

Sex Ratio (M:F)

Sample 1

0.75

0.40

0.33

0.29

Sample 2

0.44

0.81

0.67

0.91

Sample 3

0.25

0.23

0.35

0.13

Total

0.45

0.47

0.46

0.41

U. hoplurus Pocock (Scorpionidae) — were seen in small numbers only. Only the
buthid Lychas alexandrinus Hirst was collected in sufficient numbers to allow
statistical analysis (Table 1). Lychas alexandrinus is widely distributed in arid and
semi-arid Australia. It is a small animal (total length 30 mm) that, in the
sandplain environment of the Tanami Desert, shelters in abandoned burrows or
nests of other invertebrates. As only three groups of traps were used in the first
sample, the numbers of L. alexandrinus were scaled up to allow comparison with
the later samples. The numbers of individuals were transformed by natural
logarithms to normalize variances, and then a two-way analysis of variance was
conducted to compare the numbers of L. alexandrinus caught in different
vegetation states and samples.

The analysis showed that captures of L. alexandrinus did not vary significantly
with sampling time (F = 2.585, df= 2 and 12, P > 0.2), but that they did so with
vegetation state (F = 4.825, df = 3 and 12, P < 0.05); there was no significant
interaction (F = 1.085, df = 6 and 12, P > 0.5). Subsequent testing of means
with the Welsch step-up procedure failed to identify unambiguously the states
which differed, but more individuals were captured in vegetation state 2 than
states 1 and 8, with state 5 appearing to be intermediate (Table 1).

In order to look more closely at the difference between states, we examined the
condition of each scorpion by dividing the length of its carapace into the cube
root of its wet weight (we were able to do this because there was a significant
correlation between preserved wet weight and dry weight; r = 0.93). In both
males and females, these indices of condition varied significantly across the four
vegetation states; both sexes showed better condition in state 5 than elsewhere
(Table 2). These data add weight to the conclusion that populations reacted
significantly to changes in vegetation, and that the middle of the successional
gradient supported more active and relatively larger scorpions.

The sex ratio of male to female scorpions fluctuated substantially between
samples (Table 1). These discrepancies may be due to different activity patterns
between the sexes in relation to breeding, or perhaps in response to short-term
weather conditions. Although the mean ratios appeared to be similar across the

1990. The Journal of Arachnology 18:243

Table 2. — Condition of male and female Lychas alexandrinus in four vegetation states, as estimated
by dividing carapace length into the cube root of wet weight. Means ± standard deviations are shown,
with sample sizes below. Differences among states were examined with Kruskall-Wallis tests. **P <
0.01, *** P< 0.001.

Sex

Vegetation state

Chi square

Male

0.131+0.006

0.129 + 0.006

0.132 + 0.006

0.129 + 0.005

1 1.805**

Female

0.132 + 0.005

0.131 ±0.006

0.137 + 0.007

0.130 + 0.008

12.452**

Total

0.132 + 0.006

0.130 + 0.006

0.134 + 0.007

0.130 + 0.006

21.798***

113

vegetation states, our results concerning the effects of burning must be interpreted
with caution because they may be affected by patterns of foraging and
reproductive behaviors.

Although our study does not fully explain all observed changes in capture
rates, it does provide evidence that at least one species of grassland scorpion
persists readily through fires. Our data indicate that L. alexandrinus was active a
year after a fire in numbers that were statistically indistinguishable from those in
areas of mature spinifex. Increased numbers in traps were observed two to three
years after burning, and scorpions were in better condition five years after a fire.
We suspect that scorpions generally have the capacity to withstand perturbations
such as fire. Most live in burrows, either their own or those of other species, or
beneath persistent shelters (Polis 1988). It is worth noting Eastwood’s (1978)
suggestion that burrowing scorpions in South Africa were abundant after fire, but
that non-burrowing species were less likely to persist through frequent fires.
Scorpions are able to eat large quantities of food at one time and to store excess
energy in the hepato-pancreatic glands. This ability, coupled with their extremely
low metabolic rates, allows scorpions to survive without food for many months
(Polis 1988). These characteristics, together with their long life-spans, probably
allow many scorpions to avoid the direct effects of disturbances such as fire and
to take advantage of the subsequent altered conditions.

In summary, our information shows that L. alexandrinus is caught more
frequently several years after spinifex grasslands are burnt. Populations did not
appear to be reduced in numbers a year after fire, and so they seem capable of
taking advantage of the habitat changes set in train by burning.

We thank K. Jones for collecting and sorting the samples, M. Gillam, M.
Fleming, and P. Destine for assistance during the work, and A. Andersen, J.
Greenslade, G. Griffin and G. Polis for commenting on the manuscript.

LITERATURE CITED

Eastwood, E. B. 1978. Notes on the scorpion fauna of the Cape. Part 3. Some observations on the
distribution and biology of scorpions on Table Mountain. Ann. South African Mus., 74 (10):229-

248.

Griffin, G. F. 1989a. An enhanced wheel-point method for assessing cover, structure and heterogeneity
in plant communities. J. Range Manage., 42:79-81.

Griffin, G. F. 1989b. Spinifex, fire and rain. M. Sc. Thesis, Macquarie University, Sydney.

1990. The Journal of Arachnology 18:244

Morton, S. R., M. W. Gillam, K. R. Jones and M. R. Fleming. 1988. Relative efficiency of different
pit-trap systems for sampling reptiles in spinifex grasslands. Aust. Wildl. Res., 15:571-577.

Polis, G. A. 1988. Foraging and evolutionary responses of desert scorpions to harsh environmental
periods of food stress. J. Arid Environ., 14:123-134.

Polis, G. A., C. A. Myers and M. Quinlan. 1986. Burrowing biology and spatial distribution of desert
scorpions. J. Arid Environ., 10:137-146.

Warren, S. D., C. J. Scifres and P. D. Teel. 1987. Response of grassland arthropods to burning: a
review. Agric. Ecosyst. Environ., 19:105-130.

G. T. Smith, Division of Wildlife and Ecology, CSIRO, Locked Bag No. 4,
P.O., Midland, Western Australia 6056, Australia; and S. R. Morton, Division of
Wildlife and Ecology, CSIRO, RO. Box 2111, Alice Springs, Northern Territory
0871, Australia.

Manuscript received September 1989, revised February 1990.

1990. The Journal of Arachnology 18:245

BOOK REVIEW

Piatniek, N. L 1989. Advances in Spider Taxonomy 1981-1987: A Supplement
to Brigeoli’s A Catalog of the Araneae Described Between 1940 and 1981 (edited
by P Merrett). Manchester University Press. Distributed exclusively in the United
States and Canada by St. Martin’s Press, $190.00.

This magnificent 673-page volume continues the work of cataloging and
summarizing the many taxonomic changes that have occurred within the Order
Araneae since the classic works of Roewer, Bonnet, and BrignolL In his
introduction Piatniek thanks the makers of his word-processing software and
computers, and indeed the ease such tools confer on this sort of work can
scarcely be overstated. Brignoli wrote his catalog on paper slips, Piatniek wrote
his on disk. We can look ahead to that day (probably not far off) when such
works will be available in database form as well. Given the rather stiff price for
this volume and the flexible access that computers allow, that day can not arrive
too soon.

The volume is remarkably error free. The author and his able arachnologist
editor Peter Merrett deserve high praise for this. I found no errors within the
body of the catalog. In fact it corrected a long standing misunderstanding on my
part (it’s Daramulunia Lehtinen, not Daramuliana).

The bibliography is, of course, comprehensive (roughly 1200 references); as in
the catalogs of Roewer and Brignoli, only taxonomic literature is included. The
style follows that of Roewer and Brignoli in that entries are grouped first by year
rather than alphabetically by author. I personally find this style less usable, and
hope that future volumes will adopt the former style. Advances in Spider
Taxonomy resumes Roeweris formula for taxonomic entries, which delivers
succinct information on illustrations, descriptions, transfers, and synonymies. It is
fast and easy to use.

Knowing what to include and what to omit must be a problem for cataloguers.
Piatniek explains the convoluted history of araneological cataloging in his
preface. Cataloging took a severe turn for the worse when Brignoli omitted
synonymies and transfers of pre-Roewer names (those published before 1940 or
1954) from his compilation. Given that a huge number of spider names are pre-
Roewer, this omission condemned the user to just the sort of memorization of the
primary taxonomic literature that one expects catalogs to obviate. I am delighted
to report that Advances in Spider Taxonomy is back on track, and includes all
such synonymies and transfers for the time period covered. It is thus fully
comphehensive and complete. The 1940-1981 hiatus due to Brignoli’s omission
remains, but future volumes will correct this lack.

Piatniek does draw his own line, however. He omits fossils, subfamilial and
subgeneric groupings, and mentions of taxa in purely faunistic works unless
accompanied by useful illustrations. Neither does he list instances where an
author provided only general habitus illustrations. These are reasonable
pragmatic decisions that will not impede most taxonomic work.

1990. The Journal of Arachnology 18:246

That Advances in Spider Taxonomy is indispensable to researchers and
especially to taxonomists scarely needs saying, but it also provides information of
a more general nature. The Order Araeeae as a whole contains roughly 34,000
described species, grouped in 2944 genera in 105 families (N. I. Platnick, pers.
comm.). As such, it falls well within the ten most diverse ordinal groups on earth
(whatever an “order” is. . .). At the generic level Salticidae, with 490 genera,
reigns supreme. Linyphiidae is second with 386 genera. Even if one excludes
monotypic salticid and linyphiid genera, their competitors still are probably less
diverse; Thomisidae and Gnaphosidae have 160 and 141 genera, respectively.
Fourteen families remain monotypic at the generic level.

Advances in Spider Taxonomy records about 7700 taxonomic entries since
1981, including 230 newly described genera, and roughly 2581 newly described
species. (Due to possible counting errors, numbers of species reported hereafter
are rounded to the nearest ten.) Taxonomic practice seems to be improving: 1420
species were described from both sexes; 720 from females only; 440 from males
only; and just one new species was based on juvenile specimens only (in 1982).
Platnick made a special effort to cover the Soviet and Chinese literature, which
heretofore has received only spotty coverage in the West. For example, 150 of the
new species descriptions pertain to China and 180 to regions within the USSR.
As one might anticipate, the region most productive of new species is Latin
America and adjacent archipelagoes (690), followed by Africa and her islands
(320), Australia (250), North America (210), Japan and Korea (130), and India
and Sri Lanka (100). New species still turn up with respectable frequency in
Europe and adjacent Mediterranean islands (120), although discoveries in
England (that best known region) seem to be petering out at last. About a third
of all genera (1089 in 83 families) are found in the Neotropics.

This volume also conveys much about our knowledge of the phylogeny and
diversification of spider lineages. Early to nnd 20th century phylogenetic work on
spiders can be fairly summarized as cautious tinkering with Eugene Simon’s
impressionistic classification. However, in the late 1960s and early 1970s P. T.
Lehtinen and R. R. Forster showed that the old Cribellatae (which Simon
accepted) was nothing less than fictitious. This insight burst like a bomb among
araneologists, effectively shattered the complacency based on the traditional
classification, and rendered many familial and suprafamilial taxa suspect. Fast on
its heels came the more general revolution in taxonomic theory known as
cladistics, which not only corroborated the falsehood of the Cribellatae, but
undermined confidence in the existing classification (i.e., alleged taxa) even more.
By the late 1970s it is fair to say that many workers had realized that two
centuries of higher classificatory results were mostly wrong, that no supra- generic
grouping in spiders was beyond question, and that most of it would have to be
redone or at least checked. In short, the classification of Araneae has lacked any
reliable foundation for the last 20 years, despite the hollow superstructure that
persisted. This implosion of confidence affects more than mere bookkeeping.
Broad generalizations about taxon-based evolutionary or ecological process and
pattern are impossible if one’s notion of history (i.e., taxa) is awry. As is evident
from Advances in Spider Taxonomy , arachnologists will now have to get to know
major new families such as the Idiopidae (18 genera), Hexathelidae (11 genera),
Cyrtaucheeiidae (18 genera), Nemesiidae (37 genera), and Orsolobidae (27
genera), as well as major changes in recently recognized families such as

1990. The Journal of Arachnology 18:247

Cyatholipidae (7 genera) and Tetrablemmidae (30 genera). The infraordinal
classification of Mygalomorphae is completely new. Old concepts of families such
as Ageleeidae, Amaurobiidae, Clubioeidae, Dictynidae, and Hahniidae have been
altered beyond recognition. Advances in Spider Taxonomy and some ancillary
literature permits the estimate that only about 180 araneomorph genera in 22 or
23 families still contain cribellate species. Because eri bell ate taxa are likely to be
morphological relicts, they become especially important to include in phylogenetic
analyses. The comfortable but narrow view of north temperate arachnologists
continues to break apart.

Advances in Spider Taxonomy reflects this revolution. Platnick makes it quite
clear that the order followed in the catalog does not reflect his personal ideas
about spider phylogeny, and he remains uncomfortable with some of the more
anomalous groupings that still persist nomenclatorially (will someone PLEASE
sink this family?). He wisely dropped Brignoli’s effort at subfamily groupings,
who in turn wisely dropped Roewer’s efforts at supra-familial groupings. Thus all
genera within families, and species within genera, are listed alphabetically. The
order of families does still follow that of Brignoli, which is to say a one-
dimensional representation of presumed phylogenetic order. All in all, the
arrangement of Advances in Spider Taxonomy is certainly an improvement and
more realistic, since users of Roeweris catalog tend to wear out the index faster
than anything else.

Despite this retrograde trend of the past few decades, progress has been made
in discerning the phylogeny of Araneae (largely due to the taxonomic work of
Platnick and collaborators). Mesothelae and Opisthothelae are monophyletic, as
are Mygalomorphae and Araneomorphae. Within Araneomorphae two large
nested taxa seem valid: Meocribellatae and Araneoclada. From Advances in
Spider Taxonomy we find that Liphistiomorphae has just two genera, but its
sister group (by definition of equal age) has 2942. Mygalomorphae has 259, but
its sister group Araneomorphae has 2683. Within Araneomorphae the pattern
repeats itself: Paleocribellatae includes only two genera, whereas its sister taxon
Meocribellatae has 2681 genera. Finally, Araneoclada has 2671 genera. Obviously
diversification rates among spider lineages of equal age are highly dissimilar
(assuming that variation in generic size is unbiased). Within Araneoclada,
however, few large suprafamilial groupings are supported by competent
phylogenetic arguments. One can mention only Dysderoidea (99 genera, 4
families), Palpimanoidea (51 genera, 10 families), Gnaphosoidea (151 genera, 6
families), and Orbiculariae (724 genera, 13 families).

On a more frivolous level, I cannot help but note how this catalog exposes the
nomeeciatorial foibles of taxonomists. Rendering one’s phylogenetic speculations
immortal by combining the root of a pre-existing name with a small set of
particles (Alio-, Hole-, Meta-, Neo-, Para-, Proto-, Pseudo-, -aides, -iella, etc.)
seems irresistible. Like sustained stutters these etymological traditions, once
started in a family, are hard to stop. Thus Theraphosidae has always had a bad
infection of *.pelma names, Lycosidae had its *.osa names, and Ctenidae was
beset with a cacophonic diversity of *.ctenus (with apologies to DOS file-naming
conventions). The work this catalog chronicles has not been kind to this sort of
ersatz cladistic insinuation. Although Segestria cannot avoid being a segestriid, its
erstwhile nestmate Segestrioides is now a diguetid, Atypoides no longer nestles
close to Atypus. Neocteniza , alas, has fled the Ctenizidae for the Idiopidae.

1990. The Journal of Arachnology 18:248

Dysderina and Dysderoides turn out to be oonopids. At the other end of the
order, the *. poena tradition bravely begun in Theridiidae has been largely a
mysmenid phenomenon lately; even the patriarch Dipoena barely missed
expulsion from the Theridiidae (the latter swallowed the Hadrotarsidae instead).
Traditions that still endure are the *.drassus set in Gnaphosidae, and the *.nops
crowd in Oonopidae (although a fair number of the latter have broken ranks and
fled to the Caponiidae). New beginnings of this sort among leptonetids and
palpimanoids show that hope springs eternal. Nevertheless, I am personally
relieved that the ranks of *.osa in Lycosidae and * pelma in Theraphosidae have
been decimated by synonomy. The lesson of history for such semantic allusions
(and taxonomic hubris) is clear.

In sum, Advances in Spider Taxonomy is a splendid volume. I do not have to
recommend that you buy it, because you already know that it is indispensable.
Arachnologists and beyond owe Platnick fervent thanks, because few works are
as critical to good biology as nomenclatorial catalogs. If taxonomy is the sina
qua non of all biological science, it is because of works such as this.

Jonathan A. Coddington, Department of Entomology NHB 164, National
Museum of Natural History, Smithsonian Institution, Washington, DC 20560
USA.

THE AMERICAN ARACHNOLOGICAL SOCIETY

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Book Review

Advances in Spider Taxonomy 1981-1987: A Supplement to Brignoli’s
A Catalog of the Araneae Described Between 1940 and 1981
(edited by P. Merrett), by Norman I. Platnick, Jonathan A. Coddington 245

CONTENTS

THE JOURNAL OF ARACHNOLOGY

VOLUME 18 Feature Articles NUMBER 2

Annual activity patterns of the Australian tarantula

Selenocosmia stirlingi (Araneae, Theraphosidae) in an arid

area, Mandy Kotzman 123

Las especies de la subfamilia Hippasinae de America del Sur

(Araneae, Lycosidae), Roberto M. Capocasale ....131

Incorporation of urticating hairs into silk: A novel defense mechanism
in two Neotropical tarantulas (Araneae, Theraphosidae),

Samuel D. Marshall and George W.Uetz 143

Chromosomes of sixteen species of harvestmen (Arachnida, Opiliones,

Caddidae and Phalangiidae), Nubuo Tsurusaki

and James C. Cokendolpher 151

Ground surface arachnids in sandhill communities of Florida,

David T. Corey and /. Jack Stout 167

A sampling of forest-floor spiders (Araneae) by expellant, Moosehorn
National Wildlife Refuge, Maine, Daniel T. Jennings ,

W. Matthew Vander Haegen and Annie M. Narahara. 173

Population densities of spiders (Araneae) and spruce budworms
(Lepidoptera, Tortricidae) on foliage of balsam fir and red spruce in east-

central Maine, Daniel T. Jennings , John B. Dimond and Bruce A. Watt 181

A new Glenognatha (Araneae, Tetragnathidae) from New Jersey,
with redescriptions of G. centralis and G. minuta , Gustavo Hormiga

and Hartmut G. Dobel 195

Early stages of orb construction by Philoponella vicinia , Leucauge
mariana , and Nephila clavipes (Araneae, Uloboridae and Tetragnathidae),
and their phylogenetic implications, William G. Eberhard 205

Research Notes

Discovery of Caviphantes saxetorum in North America; status of Scironis

tarsalis (Araneida, Linyphiidae), Rodney L. Crawford 235

Entomophagous fungi as mortality agents of ballooning spiderlings,

Leslie Bishop 237

The effect of Hyptiotes cavatus (Uloboridae) web-manipulation on the
dimensions and stickiness of cribellar silk puffs, Brent D. Opell ,

Gabrielle Roth and Paula E. Cushing .238

Responses by scorpions to fire-initiated succession in arid Australian
spinifex grasslands, G. T. Smith and S. R. Morton 241

(continued on hack inside cover)

Cover photograph, web of Philoponella vicina
(O. Pickard-Cambridge) (Uloboridae) by Jonathan A. Coddington
Printed by PrintTech, Lubbock, Texas, USA
Posted at Lubbock, Texas, 4 October 1990

£? The Journal of

ARACHNOLOGY

OFFICIAL ORGAN OF THE AMERICAN ARACHNOLOGICAL SOCIETY

VOLUME 18

FALL 1990

NUMBER 3

THE JOURNAL OF ARACHNOLOGY

EDITOR: James E. Carico, Lynchburg College
ASSOCIATE EDITOR: Gary L. Miller, The University of Mississippi
EDITORIAL BOARD: J. E. Carrel, University of Missouri; J. A. Coddington,
National Museum of Natural History, Smithsonian Institution; J. C.
Cokendolpher, Lubbock, Texas; F. A. Coyle, Western Carolina University; C.
D. Dondale, Agriculture Canada; W. G. Eberhard, Universidad de Costa Rica;
M. E. Galiano, Museo Argentino de Ciencias Naturales; M. H. Greenstone,
BC1RL, Columbia, Missouri; N. V. Horner, Midwestern State University; D.

Uetz, University of Cincinnati; C. E. Valerio, Universidad de Costa Rica.

THE JOURNAL OF ARACHNOLOGY (ISSN 0161-8202) is published in
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Schmitt, A., M. Schuster and F. B. Barth. 1990. Daily locomotor activity patterns in three species of
Cupiennius (Araneae, Ctenidae): The males are the wandering spiders. J. Arachnol., 18:249-255.

DAILY LOCOMOTOR ACTIVITY PATTERNS IN THREE
SPECIES OF CUPIENNIUS (ARANEAE, CTENIDAE):
THE MALES ARE THE WANDERING SPIDERS

Alain Schmitt, Martin Schuster
and Friedrich G. Barth

Institut fur Zoologie, Abteilung Neurobiologie
Universitat Wien, Althanstr. 14
A-1090 Wien, Austria

ABSTRACT

The daily locomotor activity patterns of spiders of three large species of the genus Cupiennius
(Ctenidae) were measured in an artificial 12:12 light:dark cycle. Adult males ( N = 10) and females ( N
= 10) of each species of these nocturnal Central American wandering spiders were compared. On
average, males were 3.5 (C. coccineus and C. getazi) to 12.7 (C. salei ) times more active than females.
Hence, males are the truly wandering spiders. We suggest that this is due to sexually motivated
searching behavior of the males. Of the two sympatric species, the males and the females of C.
coccineus were on average 3.1 times more active than those of C. getazi. In addition C. coccineus
exhibited a relative minimum in its locomotor activity when C. getazi showed its absolute maximum.
This difference in activity pattern may contribute to the reproductive isolation of these two sympatric
species.

INTRODUCTION

In the field adult and subadult wandering spiders of the species Cupiennius
salei (Keyserling) are quite sedentary. Identified individuals were previously found
in their retreats on the same dwelling plants for at least one week (Barth and
Seyfarth 1979; Seyfarth 1980). We verified this finding during a recent stay in
Central America (Barth, Baurecht, Schmitt, unpubl. data) for C. salei and
extended its validity to C. coccineus F. P.-Cambridge and C. getazi Simon. Our
general impression, however, was that males of all three species moved around
more than the females during their nocturnal activity period.

Vibratory courtship behavior of the males of these three Cupiennius species is
released by pheromones on the silken threads of females (Rovner and Barth 1981;
Barth 1989). Hence, males must find the female silken threads and the females
themselves for reproducing. We therefore conjectured that the male might
locomote more than the female Cupiennius.

C. getazi and C. coccineus are sympatric species (Barth et al. 1988). Female
pheromones and, more importantly, male vibratory signals contribute to
reproductive isolation (Barth 1989). Differences in the daily activity patterns of
the two species might be an additional mating barrier between them.

The primary purpose of this study is to delineate the extent to which
differences in locomotor activity occur among the sexes and the species. A

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valuable byproduct of our measurements are data on the time of day to be
chosen for behavioral and physiological experiments.

MATERIAL AND METHODS

Spiders. — All spiders were laboratory bred adult males and females of three
large species of Central American nocturnal ctenids: Cupiennius salei from
Mexico, C. getazi and C. coccineus from Costa Rica (for general biology and
taxonomy see Melchers 1963; Lachmuth et al. 1984; Barth et al. 1988). 20 spiders
of each species (10 males and 10 females, all virgins) were used. C. salei males
were 14.5 ± 1.2 months old (mean ± SE) and weighed 2.43 ± 0.2 g (mean ± SE),
females were 14.3 ± 1.3 months old and weighed 3.44 ± 0.2 g. The values for C.
coccineus were 11.8 + 0.2 months and 1.73 ± 0.1 g for the males and 11.8 ± 0.4
months and 2.92 ± 0.2 g for the females. For C. getazi , the corresponding values
were 12.5 + 0.3 months and 0.94 ± 0.1 g for the males and 12.6 ± 0.2 months
and 1.5 ± 0.1 g for the females.

Activity measurements. — The activity of each individual spider was measured
continuously for 72 hours using an actograph (Animex, Farad type DSEP), the
activity registered during one 10 min period being considered as one data point.
The actograph was installed in a light-proof room with a 12:12 L:D cycle and a
temperature of 25 ± 1°C. These light and temperature conditions are similar to
those prevailing in the natural habitat of Cupiennius (Barth et al. 1988). All noisy
parts of the Animex system were kept outside the experimental room. During the
photophase the room was illuminated with fluorescent tubes (Neon-Freon type).
The spiders were transferred within their glass jars into this room at least three
days before their activity was actually monitored. This time period suffices to
entrain Cupiennius by an artificial 12:12 L:D cycle (Seyfarth 1980). All spiders
were fed four muscid flies once a week on the same day.

During the 72 hours of measurement, the spiders were kept individually in
transparent plastic cages (27X20X5 cm). We used one cage for males and another
one for females. Between trials, the cages were cleaned. Water was supplied in the
cages. During a trial the ceiling of the cage was covered with a wet cloth netting
to keep the relative air humidity at >95% inside the cage, a value often found in
the natural habitat of the spiders (Barth et al. 1988). No retreat was provided for
the spiders. The cage was shielded from direct illumination of the room and
illuminated from outside and lm above by a 60W bulb (Wolfram thread, frosted
glass, 2800° K) during the light-on phase. The light intensity inside the cage was
300 Lux. No unusual behavior of the spiders was observed after the three days of
encagement.

Calibration. — The Animex system detects the motion of the spider by
measuring the disturbance of a magnetic field. Leg movements alone are not
detected. The influence of body weight and speed of locomotion of the encaged
spider on the measurements was evaluated by the following experiments:

(a) The mean speed during bouts of spontaneous locomotion of males and
females, regardless of species varies between 5 and 89 mm/s, averaging 30 mm/s
(SD + 16 mm/s; N = 6, n = 60). A narcotized spider was moved on a piece of
cardboard by an electrically driven device over a constant distance through the
magnetic field of the Animex system at two speeds, of which the first was close to

SCHMITT EL AL.— ACTIVITY PATTERNS IN WANDERING SPIDERS

251

the above mentioned average (36 mm/s) whereas the second was higher by almost
200% (106 mm/s). This large increase in speed increased the number of impulses
registered by only 5%. Thus, this experiment demonstrated that the speed of
locomotion of the encaged spider had virtually no’ influence on the measurements.

(h) Spiders weighing 1 g and 4 g respectively, were moved at the same speed
(36 mm/s) through the magnetic field. A spider had to be moved between 26 mm
(if 4 g) and 32 mm (if 1 g) to elicit one impulse in the Animex system. Thus, an
increase in body weight by 300% increased the number of impulses registered by
roughly 23%. We corrected all the data for body weight. Body weight of each
spider remined nearly constant during the three days of measurements (weight
losses amounted to ca. 3% within one week without food).

The number of impulses registered by the Animex system was tranformed into
distance (meters) covered by the spider, using the above data.

Evaluation of data. — We calculated the total daily amount of activity [given in
meters, mean ± SE and % rel. SD = (SD/mean) X 100] and determined the
duration of the daily activity period and of the period of maximum activity.
Periods of maximum activity (dotted areas in Fig. 1) were defined as times of
scotophase during which activity of a spider exceeded 50% of the highest value
found. All individual data were compared to the mean. They were considered to
follow the mean pattern if their period of maximum activity had roughly the
same duration (± 25%) as the mean and was not shifted by more than 50% of
that duration to the left or right on the time axis. Peaks and minima of activity
were ignored in this context if they lasted for only 10 min.

RESULTS

The results of the measurements of daily activity patterns of groups of 10
spiders separated by species and sex are presented in Fig. 1. All 20 C. getazi , 18
of 20 C. salei and 13 of 20 C. coccineus showed individual activity patterns very
similar to the mean. The interindividual variability in the total amount of activity
is large: The rel. SD are between 47% (C. getazi males) and 74% (C. getazi
females, see Fig. 1, insets).

The following comments refer to the mean values. Deviations from them by
individual spiders are indicated where necessary.

General features of activity periods. — The data clearly confirm that all three
species of Cupiennius are nocturnal. Only 4.1% of the total daily activity of the
males (average of all species) and 8.7% of that of the females (average of all
species) was in the light phase. Activity begins immediately after the lights were
extinguished and within 20 min after the onset of darkness, all spiders showed
activity values larger than 50% of the absolute maximum values (Fig. 1, 1800-
1820). Thus light-off is a very effective Zeitgeber which promptly activates the
spiders. Periods of maximum locomotor activity lasted about three times longer
in males than in females (in five females of C. coccineus the period of maximum
activity lasted longer than the average, up to 0200). In both males and females
the absolute activity maxima occurred long before the end of the dark phase. The
decline was more abrupt in the male C. salei and C. coccineus than in females of
all three species and in the males of C getazi.

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>■

10 12 14 16 18 20 22 0 2 4 6 8 10 10 12 14 16 18 20 22 0 2 4 6 8 10

TIME (HOURS)

Figures la-f. Daily locomotor activity patterns of adult male and female spiders of the genus
Cupiennius (in all cases N — 10); mean (thick line) and standard error (thin line; only lower limits are
shown). The total amount of activity (m) is given by the numbers in the right upper corner (mean,
standard error and relative SD). Horizontal lines indicate 50% of maximum activity. Shaded areas
represent time periods of maximum activity. Star marks time of maximum activity in C. getazi and of
relative minimum in C. coccineus. Black area on time axis indicates dark period (1800 to 0600).

Interestingly, both male and female C. coccineus became relatively inactive at
the same time during the dark phase, i.e. between about 1900 and 2000 (see star
in Fig. lc,d). After 1-2 h they resumed activity to almost the same degree as at
the onset of the scotophase.

The time course of the activity of adult C. salei females in our present
experiments was similar to that previously reported by Seyfarth (1980) for
subadult females of the same species. As is known from Seyfarth’s (1980)
experiments, this activity pattern reflects a biorhythm.

SCHMITT EL AL.— ACTIVITY PATTERNS IN WANDERING SPIDERS

253

Differences between the sexes. — The average total amount of locomotor
activity of males was 3.5 (C coccineus and C. getazi) and 12.7 (C. salei) times
larger than that of females (Fig. 1). Periods of female maximum activity fell
within the periods of maximum male activity (Fig. 1). However, the males of C
getazi continued to move around at a high rate for about 4 hours and those of C.
salei and C. coccineus for about 7 hours after the end of the period of female
maximum activity (Fig. 1).

The following deviations of individuals of C. coccineus from the mean C
coccineus activity patterns were observed. Three of the females exhibited 5 to 8
activity maxima with zero activity in between instead of a relative minimum at
the usual time between about 1900 and 2000. The four exceptional males , on the
other hand, had their locomotor activity evenly distributed between about 1800
and 0400.

Differences between sympatric species. — The activity periods of the two
sympatric species, C. coccineus and C. getazi , partly overlap, i.e., there was no
allochrony (Fig. Ic-f). Apart from the fact that C. coccineus males and females
were on average 3.1 times more active than C. getazi males and females, three
remarkable features of the activity patterns of these two species emerge.

(/) C. getazi males and females had their absolute activity maxima between
1830 and 2230 and between 1830 and 1930, respectively (star in Fig. le,f). During
the same time period, C. coccineus males (1900 to 2030) and females (1830 to
2000) exhibit a relative minimum in their activity patterns (star in Fig. lc,d).
Absolute activity values of both species were similar during that time period (for
exceptions see preceding section).

(if) The activity of C. coccineus males is distributed over nearly the whole dark
phase of 12 hours (but see relative minimum, above), whereas C. getazi males are
only active during the first 8 hours of the dark phase. Correspondingly, the
female activities last longer in C. coccineus (from about 1800 to 0200, but see
minimum, above) than in C. getazi (about 1800 to 0200).

{iii) C. coccineus spiders were most active when the activity of C. getazi was
already decreasing (Fig. lc-f).

DISCUSSION

Thre are several studies on biorhythms of spiders which have been the subject
of a recent review by Cloudsley-Thompson (1987). To our knowledge, however,
so far no data are in the literature on sex-related differences in the amount of
locomotor activity. Likewise, no comparative data on the activity patterns of
closely related spider species are available.

Differences between the sexes. — Field observations on population structure and
laboratory studies on courtship behavior of Cupiennius (Rovner and Barth 1981;
Barth 1989) suggest that sexually motivated searching behavior is the main factor
causing the differences in amount of locomotor activity between males and
females. Antipredatory behavior and search for prey or a retreat might be
additional or alternative factors influencing locomotor activity. The following
arguments are considered as evidence against their importance in the given
context.

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(/) Predators : The spiders were not exposed to predators nor disturbed by any
obvious stimuli from outside during the measurements. Even if unnoticed stimuli
would have been present, they should have influenced males and females in a
similar way and therefore cannot account for the observed differences between
the sexes.

(ii) Search for prey : All spiders were fed according to the same regime with no
feeding during the time of measurements. Cupiennius is a sit-and-wait predator
(Melchers 1963; Barth and Seyfarth 1979). The spiders of all three species come
out of the retreat at dusk as first described by Barth and Seyfarth (1979), and, as
a rule, move less than one meter on their dwelling plant (pers. obs. Barth,
Baurecht, Schmitt). There are no known differences in predatory behavior
between males and females. There is no indication that the search for prey could
account for the differences in locomotor activity between the sexes.

(Hi) Retreats’. Retreats of the females are often found to be partly or completely
closed by compact web sheets. This is never observed for males, neither in the
laboratory nor in the field. Females build their egg sacs and take care of them for
about three weeks while in their retreats. Spiderlings often hatch within the
retreat and live there for about one week before they disperse. We assume that
retreats are more important for females and that they might therefore search
more intensively for adequate retreats than males when held in barren cages.
Despite the complete absence of retreats in the cages, the males were the much
more active sex.

Differences between sympatric species. — The number of interspecific encounters
in sympatric species is not only determined by their spatial proximity or distance
and by their absolute amount of activity, but also by the degree of temporal
overlap of their activity periods.

Our data suggest that activity patterns may indeed contribute to reproductive
isolation of the two sympatric species, C. coccineus and C. getazi. The probability
of encountering each other is reduced because (i) C. coccineus has a relative
minimum during the time period of the absolute activity maximum of C. getazi
and (ii) C. coccineus is most active when the activity of C. getazi is already
decreasing.

The few individual deviations from mean activity patterns do not weaken the
above conclusions since temporal isolation has to be considered as a parameter
describing two or more groups of individuals (populations) and not single
individuals. Thus, mean (population) patterns have to be compared.

Differences in the amount of activity among the three species. — Interspecific
differences in total amounts of activity are hard to interpret with the limited
knowledge at hand. They could reflect differences in population density, the
males of the species with greater population density being less active because of
higher chances for finding a female. Data from our field work show, however,
that, given similarly high dwelling plant densities, population densities of the
three Cupiennius species are similar (Barth, Baurecht, Schmitt in prep.).

The rather high absolute values of total amount of activity found in our
experiments should not simply be transferred to the primary forest situation. We
instead suggest that the activity was particularly high in our cage situation
because of the unattractive environment with no retreat, no prey, no sexual
partner and no dwelling plant.

SCHMITT EL AL.— ACTIVITY PATTERNS IN WANDERING SPIDERS

255

ACKNOWLEDGMENTS

We thank G. Hofecker and H. Bubna-Littitz (Institut fur Physiologic,

Veterinarmedizinische Universitat Wien) for kindly providing the Animex system.

We are grateful for the comments of J. E. Carrell, J. S. Rovner and an

anonymous reviewer on the manuscript. Supported by a grant of the Fonds zur

Fdrderung der Wissenschaftlichen Forschung Austria, to FGB (project P6769B).

LITERATURE CITED

Barth, F. G. 1989. Sensory guidance in spider pre-copulatory behaviour. In Sensory Guidance in
Invertebrate Behaviour. (W. J. P. Barnes, ed.). Manchester Univ. Press, Manchester (in press).

Barth, F. G., E-A. Seyfarth, H. Bleckmann and W. Schtich. 1988. Spiders of the genus Cupiennius
Simon 1891 (Araneae, Ctenidae). I. Range distribution, dwelling plants, and climatic
characteristics of the habitats. Oecologia, 77:187-193.

Barth, F. G. and E-A. Seyfarth. 1979. Cupiennius salei Keys. (Araneae) in the highlands of central
Guatemala. J. Arachnol., 7:255-263.

Cloudsley-Thompson, J. L. 1987. The biorhythms of spiders. Pp. 371-379. In Ecophysiology of
Spiders. (W. Nentwig, ed.) Springer, Berlin.

Lachmuth, U., M. Grasshoff and F. G. Barth. 1984. Taxonomische Revision der Gattung Cupiennius
Simon 1891 (Arachnida: Araneae). Senckenbergiana Biol., 65:329-372.

Melchers, M. 1963. Zur Biologie und zum Verhalten von Cupiennius salei (Keyserling), einer
amerikanischen Ctenide. Zool. Jahrb. Abt. Syst. Okol. Geogr. Tiere, 91:1-90.

Rovner, J. S. and F. G. Barth. 1981. Vibratory communication through living plants by a tropical
wandering spider. Science, 214:464-466.

Seyfarth, E-A. 1980. Daily patterns of locomotor activity in a wandering spider. Physiol. Entomol.,
5:199-206.

Manuscript received November 1989, revised February 1990.

Fernandez-Montraveta, C. and J. Ortega. 1990. Some aspects of the reproductive behavior of Lycosa
tarentula fasciiventris { Araneae, Lycosidae). J. Arachnol., 18:257-262.

SOME ASPECTS OF THE REPRODUCTIVE BEHAVIOR
OF LYCOSA TARENTULA FASCIIVENTRIS
(ARANEAE, LYCOSIDAE)

C. Fernandez-Montraveta and J. Ortega

Departamento de Psicologia Biologica y de la Salud
Universidad Autonoma. Cantoblanco
28049-Madrid, Espana

ABSTRACT

The duration of the reproductive and courtship periods, the number of individual matings, and the
number of egg sacs and their viability were measured in Lycosa tarentula fasciiventris under
laboratory conditions. We found that the reproductive period is very short, lasting for a month from
July to August. Both the males and the females can mate more than once. Female receptivity is
related to age and reproductive state: receptivity is less in both old and previously mated females.
Neither the size nor the viability of cocoons is related to the number of female matings. Our results
are interpreted in relation to optimization of egg fertilization.

RESUMEN

En Lycosa tarentula fasciiventris , hemos medido la duracion del periodo reproductivo y del cortejo,
el numero de apareamientos de cada individuo, el numero de puestas de cada hembra y su viabilidad
en el laboratorio. Hemos encontrado que el periodo reproductivo es muy breve, de alrededor de un
mes, comprendido entre julio y agosto. Tanto los machos como las hembras se aparean mas de una
vez, estando relacionada la receptividad de la hembra con su edad y con su estado reproductivo: tanto
las hembras “viejas” como las previamente apareadas muestran una receptividad menor. Ni el tamaho
ni la viabilidad de la puesta estan relacionados con el numero de apareamientos realizados por la
hembra. Nuestros resultados se interpretan en relacion a la optimization de la fertilization de los
huevos.

INTRODUCTION

Theoretical models which try to explain the reproductive tactics of males and
females have been developed which usually refer to species in which both the
number of eggs produced by females and the investment of the male in the
offspring are very low (Gould 1982; Huntingford & Turner 1987). It has been
predicted that females will try to invest in only a few matings, will take less
advantage of multiple mating, and will choose the male with which to mate
(Halliday 1983, 1986; Huntingford & Turner 1987), whereas males will compete
for females.

Lycosa tarentula fasciiventris Dufour is a burrowing spider from the Iberian
peninsula. In central Spain, populations are distributed in open and arid areas

(Barrientos 1978) with poor plant cover. Temperature conditions are greatly

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variable, both seasonally and daily. Animals live in burrows throughout all their
developmental stages, except the adult males, with adult females showing the
greatest location stability (pers. obs.). Individual development takes place over a
period of about 22 months, and animals reach their adult instar at about the end
of spring in their second year of life. Reproduction takes place shortly after, at
the beginning of the summer (pers. obs.). During this time, males are found
wandering in search of females in areas in which isolated individuals are very
distant from one another. Male survival after the reproductive period is nil,
whereas females may survive for several months. Under laboratory conditions,
males may live as long as 2 or 3 months after summer, while females may live as
much as 1.5 to 2 years. Like many other spider species (Fink 1986), females show
a kind of behavior towards their egg sac that has been called “maternal” (Horel &
Krafft 1986). They carry with them both their egg sac and their spiderlings, thus
leading to changes in female responsiveness (pers. obs.).

The interindividual distances will make the chance of finding a mate low for
both the males and females. Under these conditions, males might be expected to
compete for females. However, laboratory observations have shown male
agonistic interactions being settled in a ritualized way and leading to apparently
paradoxical results (smaller or intruder male wins). Given the fact that female
longevity is higher, postcopulatory guarding behavior is not to be predicted
(Austad 1984). Competition between females might also be expected (Fernandez-
Montraveta & Ortega, in press), as well as female choice, given that female
investment is greater than in the male.

In this paper we try to measure some reproductive behavior variables in order
to evaluate how they fit the expected patterns according to whether or not
animals are behaving in ways that lead to relatively high reproductive payoffs.

MATERIAL AND METHODS

In this study, 71 adult males and 66 adult females were used. Alll the animals
were from the countryside around the “Universidad Autonoma de Madrid”. All
the males and 56 females were collected during the spring of 1985 and 1986, when
immature, usually at their penultimate developmental stage. The remaining
females (10) were collected as adults around the end of winter, 1985. Animals
were kept isolated under controlled conditions of temperature (25 ± 5°C), 10:14
lighudark cycle, and fed twice weekly with a blowfly outside the observation
periods.

Animals were observed in their adult stage. The observation chamber was a
terrarium occupied both by the male and the female for a week before the
observation took place. Previous to the observation, animals were visually
isolated from one another; the partition was removed to carry out the
observation. We used only males having molted to adults during the year of the
study, 37 females having also molted during this year (“young females”) and 29
adult females 1 year old when the observation took place (“old females”). This
last group comprised both the animals collected when adults, presumably
“copulated females”, and animals collected when immature that have not
copulated during their first adult year (“virgin females”). The decision to consider
the first group of females as copulated ones was made a posteriori : all of these
animals later constructed a viable egg sac, without copulating, in the laboratory.

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259

During July and August of both 1985 and 1986, we observed 254 pairs of
animals. Pairs were formed at random with regard to individual variables. Every
animal was observed at first through the first week after molting, and at least
twice on different days. If copulation occurred, the second observation was made
during the first week after copulation and so on. Each observation lasted at least
30 min. Females were usually inside their burrow, so interaction took place there.
We have considered that interaction began when the male was 2 or 3 cm away
from the female burrow, and oriented towards it. When an interaction took place,
the observation was prolonged as long as it lasted. Interaction finished when the
male moved away from the female nest and ceased orientation. Ninety-five
interaction sequences were obtained and analyzed. After the observation period,
animals were kept in the laboratory and observations about the subsequent
reproductive activity were made.

We measured (i) the date on which molting to adulthood took place, (ii) the
date of copulation, (iii) the result (copulation/retreating before copulation) of
interactions, (iv) the number of matings for both sexes, (v) the courtship and
copulation durations, (vi) the number of egg sacs for every female, (vii) the
weight of each egg sac and (viii) the number of spiderlings emerging from each
egg sac. Results have been compared with regard to four female groups, two
related to female age (young females/ old females) and the other related to their
previous reproductive history (virgin female/ copulated female).

As for quantitative variables, their mean values and standard deviations have
been calculated. In order to compare the means, a variance homogeneity test was
made before applying the t- test.

In order to measure how the quantitative variables are related, the correlation
coefficient was calculated and the Chi-square test was applied to measure the
independence of the results with regard to the different female groups.

RESULTS

In 1986, both male and female molting in the laboratory reached a peak about
the second week of June. In 1985, the same peak was observed about the third
week of June in males and the second week of July in females. Copulation was
observed from the middle of June to the first week of August, and the copulation
rate increased steadily with time. Peaks were observed at the end of July (1986)
and the beginning of August (1985).

Forty-six copulations were observed in all. When in the second year of their
adult life, only 42% of the females were receptive if virgin, as contrasted to 81%
of the young virgin females. The old, previously mated females were not receptive
at all (Table 1). We tested the dependence between receptivity and “age” and
“previous reproductive history” separately. Female receptivity significantly
depends on the female’s previous reproductive history (x2 — 5.53, p < 0.05);
virgin females were receptive in 68% of the cases in contrast to 39% of the
previously copulated females. It also depends significantly on age (x2 — 19.80, p
< 0.05); 78% of the females were receptive when young and only 28% when old.

Forty-eight per cent of the males observed succeeded in copulating, in contrast
to 68% of the females. Both the males and the females can mate more than once
under laboratory conditions (Table 2). Sixty-five percent of the males copulated

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Table 1. —Female receptive response to mating with regard to its age and its previous reproductive
history (PRH).

Variable

Receptive Respo

nse

Total

PRH

Age

Yes

Virgin

young

old

Copulated

young

old

Total

once and 35% twice, but no male copulated more than twice. Among the females,
82% were receptive only once, 16% twice and 3% more than twice.

Mean courtship duration was 23.4 ± 21.25 min. The mean duration when the
courted female was virgin, regardless of age, was 17.6 ± 17.34 min. The mean
courtship duration when females were young virgins was 20.1 ± 20.35 min, and
15.3 ± 13.70 min when old virgins {t = 0.42, ns). The mean courtship duration
when the female was young and had previously copulated was 25.0 ± 16.26 min
and 40.7 ± 28.77 min when the courted females were old, previously copulated
ones. There is a statistically significant difference between the mean courtship
duration of the virgin group, regardless of age, and the old, previously copulated
group (/ = 2.14, p < 0.05). The observed mean copulation duration was 89.2 ±
31.1 min.

Data from 35 first egg sacs were analyzed. Of these, 30 were from females
having copulated once and five from females having copulated twice or more.
Mean weight of the egg sacs was 0.30 ± 0.10 g in the first group and 0.22 + 0.06
g in the second (/ = 1.60, ns). We observed no greater size in the egg sacs of
females that copulated more than once. Spiderlings emerged from 21 egg sacs in
the first case and three in the second. Mean number of emerged spiderlings was
1 17.2 ± 51.8 in the first group, and 105.67 + 31.41 in the second. The correlation
coefficient between egg sac weight and number of living spiderlings was 0.61 {p <
0.05).

There were 20 second egg sacs, both by females collected as adults and by
females kept in the laboratory for more than 1 year. The second egg sac was then
produced in the second year the females lived, not being preceded by mating
during that year. Living spiderlings emerged from 10 of them (50%).

DISCUSSION

We measured some synchronization between the molting dates of males and
females, providing mating is concentrated during a very short period of time. We

Table 2. — Number of males and females copulating once, twice, or more than twice.

Sex

Number of matings

Total

Male

Female

Total

FERNANDEZ & ORTEGA REPRODUCTIVE BEHAVIOR OF LYCOS A

261

consider that the difference observed between the two years might indicate that
the individual molting date is adjusted to the changing environmental factors.
Since animals for the most part were captured shortly before their molt to adults,
we think these factors could have affected individual molting dates.

The nature of the factors determining female receptivity, related to its age and
previous reproductive history, might explain the observed shortness of the period
in which mating took place. This time limitation suggests that competition
between males is reflected in their early maturation rather than by direct
aggression, accounting for the earlier maturation peak shown by males, especially
in our first year of study. This hypothesis might also explain the apparently
paradoxical resolution of male interactions we observed in this species.

Both the males and the females we observed can achieve more than one
mating, as do many other spider species (Jackson 1979; Austad 1984; Christenson
1984; Breene & Sweet 1985; Brown 1985). Our results do not suggest multiple
mating to be related to greater success of the first female egg sac in this species.
Since sexual partners seem to be limited, the multiple-mating benefit for females
might be related to the sperm supply (Austad 1984; Christenson 1984), given the
egg sac size and the need for sperm to be stored in order to be successively used
(Christenson et al. 1985). The greater cost of rejecting a persistent male rather
than accepting copulation as the reason for this multiple mating (Austad 1984;
Christenson et al. 1985) does not seem to be the most appropriate explanation
because non-receptive females of this species are rather aggressive (Ortega et al.
1986), like other lycosid females (Rovner 1972). The need for a sperm supply,
along with the possible benefit of genetic diversity among offspring (Christenson
1984; Huntingford 1984; Huntingford & Turner 1987) could be the reason why
female reproductive strategy consists of accepting matings with several males
during one reproductive period.

Female sperm storage, as well as multiple egg sacs seems to be a general
pattern in spiders (Austad 1984; Christenson 1984; Blandin & Celerier 1986; Fink
1986). Mating also takes place before the first oviposition in other spider species
(Austad 1984; Sadana pers. com.). The advantages of this species concentration
of mating in only one reproductive period should be explored. We think this
concentration might be a consequence of the great seasonal climatic differences,
given the lesser inter-egg sac period shown by other lycosid spiders.

Since, in the species we have studied, female investment is greater than the
male’s, female choice should be expected (Huntingford 1984). With regard to the
kind of individuals with which a female mates, its behavior when virgin does not
seem to be discriminative (Ortega et al. 1986). Female choice has been postulated
in a few cases (Austad & Thornhill 1986), as taking place when females have
already copulated (Jackson 1982). This is interpreted as first mating guaranteeing
egg fertilization, offspring quality being increased in the following matings
(Halliday 1983). The occurrence of multiple mating with lesser receptivity of
previously mated females agrees with that prediction.

The duration of male courtship with regard to female reproductive status might
indicate male behavior is based on investing a fair amount of time courting every
female found, even if she does not show any receptive response at first (Ortega et
al. 1986).

To reach the adult stage early and to succeed in mating with all the females he
finds would define the male reproductive tactic. Females, on the other hand, will

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try to choose the male to mate with after the sperm supply has been guaranteed,
and to reduce the copulation duration to the effective insemination period.
Conflict of interests will arise over these factors. Males are expected to prolong
the copulation duration beyond the effectiveness of insemination, whereas females
are expected to try to reduce the total copulation duration to just the effective
insemination periods. More data on copulation in this species is needed to test
this hypothesis.

ACKNOWLEDGMENTS

Thanks to T. E. Christenson and an anonymous reviewer for their valuable
comments on this manuscript, which have improved it.

LITERATURE CITED

Austad, S. N. 1984. Evolution of sperm priority patterns in spiders. Pp. 223-249, In Sperm
Competition and the Evolution of Animal Mating Systems. (R. L. Smith, ed). Academic Press,
New York.

Austad, S. N. and R. Thornhill. 1986. Female reproductive variation in a nuptial-feeding spider,
Pisaura mirabilis. Bull. British Arachnol. Soc., 7:48-52.

Barrientos, J. A. 1978. Contribucion al estudio de los araneidos licosiformes de Cataluna. Tesis
Doctoral. Univ. Autonoma: Barcelona.

Blandin, P. and H. L. Celerier. 1986. L etude des strategies demographiques chez les araignees. Mem.
Soc. Beige Ent., 33:25-35.

Breene, R. G. and M. H. Sweet. 1985. Evidence of insemination of multiple females by the male black
widow spider, Latrodectus mactans (Araneae, Theridiidae). J. Arachnol., 13:331-336.

Brown, S. G. 1985. Mating behavior of the golden-orb weaving spider Nephila clavipes. II: Sperm
capacitation, sperm competition and fecundity. J. Comp. Psychol., 99:167-175.

Christenson, T. E. 1984. Alternative reproductive tactics in spiders. Amer. Zool., 24:321-332.
Christenson, T. E., S. G. Brown, P. A. Wenz, E. M. Hill and K. C. Goist. 1985. Mating behavior of
the golden orb-weaving spider Nephila clavipes. I: Female receptivity and male courtship. J.
Comp. Psychol., 99, 2:160-166.

Fernandez-Montraveta, C. y J. Ortega in press. El comportamiento agonistico de hembras adultas de
Lycosa tarentula fasciiventris (Araneae, Lycosidae). J. Arachnol.

Fink, L. S. 1986. Costs and benefits of maternal behaviour in the green lynx spider (Oxyopidae,
Peucetia viridans). Anim. Behav., 34:1051-1060.

Gould, J. L. 1982. Ethology. The Mechanisms and Evolution of Behaviour. Norton, New York.

Halliday, T. R. 1983. The study of mate choice. Pp. 3-33, In Mate Choice. (P. Bateson, ed.).
Cambridge Univ. Press, Cambridge.

Halliday, T. R. 1986. Courtship. Pp. 80-86, In The Collins Encyclopedia of Animal Behaviour. (P. J.
B. Slater, ed.). Collins, London.

Horel, A. and B. Krafft. 1986. Le comportement maternel chez les araignees et son intervention dans
les processus sociaux. Comportements, 6:17-29.

Huntingford, F. 1984. The Study of Animal Behaviour. Champan & Hall, London.

Huntingford, F. and A. Turner. 1987. Animal Conflict. Chapman & Hall, London.

Jackson, R. R. 1979. Comparative studies of Dictyna and Mallos (Araneae, Dictyniidae). II: The
relatiorishhip between courtship, mating, agression and cannibalism in species with differing types
of social organization. Rev. Arachnol., 2:103-132.

Jackson, R. R. 1982. The behavior of communicating in jumping spiders (Salticidae). Pp. 213-248, In
Spider Communication. Mechanisms and Ecological Significance. (P. N. Witt and J. S. Rovner,
eds.) Princeton Univ. Press, Princeton.

Ortega, J., C. Fernandez and E. Pablos. 1986. Comportamiento sexual en Lycosa tarentula
fasciiventris Dufour (Araneae, Lycosidae). Pp. 103-106, In J. A. Barrientos (Ed.). Actas X Congr.
Int. Aracnol., Jaca/Espana.

Rovner, J. S. 1972. Copulation in the lycosid spider Lycosa rabida Walckenaer: a quantitative study.
Anim. Behav., 20:133-138.

Suter, R. B. 1990. Determinants of fecundity in Frontinella pyramitela (Araneae, Linyphiidae), J.
Arachnol., 18:263-269.

DETERMINANTS OF FECUNDITY IN
FRONTINELLA PYRAMITELA (ARANEAE, LINYPHIIDAE)

Robert B. Suter1

The Rockefeller University Field Research Center
Tyrrel Road

Millbrook, New York 12545 USA

ABSTRACT

The fitness of Frontinella pyramitela (Walckenaer) (Araneae, Linyphiidae) is, by definition, a
function of its lifetime fecundity and the survivorship of its offspring. In the present study, I sought
the major determinants of fecundity in a laboratory setting and then evaluated the results in the
context of several published field studies. According to this analysis, the primary determinants are
female longevity, foraging success, and size. The data also permitted the calculation of an expected
relative contribution to total fecundity of each clutch of eggs: because the fertility rate drops sharply
after the second clutch is deposited, early mortality is disproportionately detrimental to lifetime
fecundity.

INTRODUCTION

Darwinian fitness, despite its succinct definition, is notoriously difficult to
assess in living organisms (Endler 1986) because three of its principal
components, age at first reproduction, lifetime fecundity, and survivorship of
offspring (Vehrencamp and Bradbury 1984; Horn and Rubenstein 1984), can
seldom all be measured. Nevertheless, differences among animals in any one
component are likely to be strongly correlated with differences in fitness, and thus
it has become common to study fecundity (number of live births), for example, as
an index of fitness (e.g., Emlen and Wrege 1988; Riechert and Tracy 1975).

Scattered in the arachnological literature are numerous reports on aspects of
spider fecundity such as eggs per clutch, time between clutches, and fertility. The
earlier studies have been reviewed by Turnbull (1973). In more recent literature, a
number of authors have reported that ecological variables such as photoperiod
(Miyashita 1987a) or foraging success (Riechert and Tracy 1975; Wise 1979;
Morse and Fritz 1987), and individual variables such as female size (Fritz and
Morse 1985; Killebrew and Ford 1985), contribute to observed intraspecific
variability in spider fecundity. Other reports, taken together, have demonstrated
the plurality of spider responses to ecological variables: ambient temperature
appears not to influence fecundity in one theridiid, Achaearanea tepidariorum (C.
L. Koch) (Miyashita 1987b), but has a strong influence in another, Theridion
rufipes Bryant (Downes 1988); similarly, food deprivation does not affect the
number of eggs produced either by a linyphiid, Linyphia triangularis (Clerck)
(Turnbull 1962), or by some species of the lycosid genus Pardosa (Kessler 1971),

1 Present Address: Department of Biology, Vassar College, Poughkeepsie, NY 12601 USA.

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but it does affect the number of eggs produced by other Pardosa species (Kessler
1971) and by a thomisid, Misumena vatia (Clerck) (Fritz and Morse 1985). This

variety of responses to the same environmental variables suggests that it may be
unwise to generalize (Eberhard 1979).

In the laboratory investigation reported below, I attempted to discover the
primary determinants of fecundity in the bowl and doily spider, Frontinella
pyramitela (Walckenaer) (Linyphiidae). This spider is a small, nearly ubiquitous
inhabitant of fields and shrublands in temperate North America. It has been the
subject of numerous ecological (e.g., Janetos 1983; Suter 1985), ethological (e.g.,
Hodge 1987; Austad 1983; Suter and Parkhill 1990), and biophysical (e.g.,
Pointing 1965; Suter 1984; Suter et al. 1987) investigations.

MATERIALS AND METHODS

In May of 1988 I captured immature male and female F pyramitela from their
webs in old fields in Dutchess County, NY. The spiders were reared to adulthood
in isolation from their conspecifics in 473-ml plastic containers at 100% RH,
approximately 12:12 photoperiod, and 22=24 °C. They were maintained on a diet
of live vinegar flies ( Drosophila melanogaster), and mean feeding rates varied
between 0.62 and 1.55 flies per day (0.81 to 2.02 mg/d). The variation was
attributable in part to the spiders’ prey capture success and in part to an
interaction between the feeding schedule and the timing of ovipositions (feeding is
inhibited for 1 to 2 days prior to oviposition). The range of feeding rates brackets
Austad ’s (1989) field estimate of foraging success (1.48 mg/d, equivalent to eight
D. melanogaster per week) and is lower than my own direct field measure of
foraging success (Suter 1985: median = 3.12 mg/d). Females were virgins at the
beginning of the study and were allowed only a single mating which occurred
within 7 days of the molt to adulthood.

I recorded the matings on videotape (at 2 fps) and then removed the males.
The videotaped images provided accurate information about the duration of the
insemination phase (Austad 1982; Suter and Parkhill 1990) of each mating.
Females that deposited eggs fertilized in those matings (N = 57) were transferred
to new containers after each oviposition, and their egg cocoons ( N = 169) were
maintained under the conditions outlined above. Egg cocoons were transferred to
70% ethyl alcohol eleven days after oviposition and subsequently analyzed with
respect to number of progeny (well-developed eggs or hatched spiderlings), size of
progeny (Suter and Parkhill 1990), and unfertilized eggs (no visible evidence of
tissue differentiation).

Fourteen pairwise relationships among the variables were evaluated using
regression statistics, with a = 0.01 because of the large number of tests. The
resulting probabilities were used not to reject explicit hypotheses but rather as a
guide to important relationships. Multiple regression of copulation duration,
number of clutches, and female mass on lifetime fecundity was not performed
because the number of females on which all three independent variables were
available was small (18).

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265

Table 1. — Components of fecundity in E pyramiiela. Number of progeny, latency to oviposition,
and productivity were tested for relationships with other variables. For those comparisons in which
the coefficient of determination was significant ( P < 0.01), the sign of the slope of the tested line is
indicated in parentheses.

Relationship

Total progeny versus copulation duration
(see Suter and Parkhill 1990)

0.004

0.742

Total progeny versus total number of
clutches

0.458 (+)

<0.001

Progeny per clutch versus post-oviposition
mass of female

0.348 (+)

0.001

Progeny (I) versus feeding rate
(flies/ day between insemination and
first oviposition)

0.263 (+)

<0.001

Progeny (II) versus feeding rate
(flies/ day between first and second
ovipositions)

0.314 (+)

<0.001

Progeny (II) versus latency (II)

(second oviposition data only)

0.110

0.020

Latency (I) versus food consumption
(time and flies consumed between
insemination and first oviposition)

0.037

0.179

Latency (I) versus post-oviposition mass
of female

0.282 (+)

0.004

Latency (II) versus food consumption
(time and flies consumed between first
and second ovipositions)

0.136 (+)

0.008

Latency (II) versus post-oviposition mass

0.009

0.637

Latency (III) versus food consumption
(time from insemination, flies between
last molt and first oviposition

0.038

0.182

Eggs per clutch versus dutch order

169

0.365 (-)

<0.001

Productivity (I, eggs/ feeding rate) versus
post-oviposition mass of female

0.005

0.972

Productivity (II, eggs/ feeding rate) versus
post-oviposition mass of female

0.067

0.181

RESULTS

The results of this study are summarized in Table 1. Of the 14 relationships
tested, six were significant (P < 0.01) and had positive slopes. (1) Spiders that
lived for many weeks after insemination produced more clutches, and
consequently more live progeny, than did spiders that died soon after
insemination. Figure 1 characterizes the variation in this relationship between
total fecundity and number of clutches produced. (2, 3) The feeding rate achieved
by a female strongly affected the number of progeny produced in the immediately
succeeding clutch for both the first and second clutches. (4) The number of live
progeny in each clutch was strongly related to the mass of the female after
oviposition. (5) Larger female mass also increased the delay between insemination
and first oviposition, but mass differences were not related to differences in the
latency to the second oviposition. (6) Latency to the second oviposition was
strongly related to food consumption during the same period, an uninteresting

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Figure 1. — The fecundity of bowl and doily
spiders (lower panel) is closely tied to the number
of clutches produced (r2 = 0.458), which is in turn
closely related to longevity. This relationship exists
despite the rapid decrease in fertility that occurs
after the second clutch is deposited (upper panel,
and see Suter and Parkhill 1990). Much of the
variation seen in the lower panel is probably
attributable to the consequences of differences
among females in mass and food consumption
(Table 1).

Total Clutches

consequence of the fact that animals with shorter latencies had fewer days during
which to capture prey.

One other relationship was significant but had a negative slope: (7) With
respect to number of eggs per clutch, earlier clutches contained more eggs than
did later clutches (ANOVA, F = 5.97, P < 0.001) although most of that variation
was due to higher numbers in first clutches (mean ± SD clutch size for all
clutches, 42.12 ± 14.40, N = 169; for first clutches, 53.32 ± 14.37, N = 57);
Bonferroni simultaneous confidence intervals for all comparisons in the ANOVA
show that only the first clutch is significantly different, at the 0.05 level, from the
grand mean). This relationship was previously reported for this species by Austad
(1982,1989).

The latency to oviposition for the first clutch (I) was measured from the date of
insemination whereas the latency to oviposition for the second clutch (II) was
measured from the date of the first oviposition. It is perhaps not surprising,
therefore, to find that latency I was significantly shorter than latency II (I, mean
± SD, 9.62 ± 3.2, N = 47; II, 11.83 ± 3.26, N = 47; t = 3.41, P = 0.001),
because a female probably begins to synthesize yolk prior to insemination.
Similarly, productivity (measured as eggs produced relative to the food intake
rate), is lower for the second clutch than for the first, probably because the first
clutch contains some pre-insemination yolk [first, mean ± SD, 50.51 ± 14.42
eggs/ (flies/ day), N ± 47; second, 39.01 ± 12.99, N= 54; t = 4.44, P< 0.0001].

Eggs per clutch varied linearly with feeding rate over the range of feeding rates
(0.81 to 2.02 mg/d) in this study, with a slope of 32 eggs/(mg/d). Thus over the
mean 1 1.8 days between clutches, a spider could produce about 2.7 eggs per mg
of prey mass consumed.

Clutch Number

SUTER— FECUNDITY IN BOWL AND DOILY SPIDERS

267

DISCUSSION

The data presented above elucidate the primary determinants of lifetime
fecundity in F pyramitela in a laboratory setting: longevity, size, and feeding rate.

Longevity. — Animals that live longer have more opportunities to reproduce,
usually, than those that live only briefly. In animals that reproduce repeatedly,
lifetime fecundity is particularly 'sensitive to variation in survivorship. Because the
bowl and doily spider is itero parous, it is not surprising to find that females that
live longer produce more clutches and more eggs (Fig. 1, Table 1). In the
laboratory, these spiders deposit up to five clutches containing about 42 eggs per
clutch [approximately twice the clutch size reported by Austad (1982), but very
close to field reports by Austad (1989)] at approximately 11 -day intervals.
Fertility declines rapidly after the second clutch (Fig. 1) although egg production
does not. The sharp decline in fertility after the second clutch (also reported by
Austad 1982, 1989) may indicate sperm depletion or senescence, egg senescence,
or some combination of these factors.

The implications of these data can be assessed in the context of field
survivorship of F pyramitela . Austad (1989) has reported that in field studies,
females have surprisingly high mortality rates: his data indicate losses equivalent
to 13.5% of the population per day (a probability of mortality of 0.135 per adult
female per day). The estimate is about four times higher than my own
calculations (0.035 per adult female per day, unpublished data) based on a field
demographic study (Suter 1985). Using as bases for calculations the average
oviposition latencies reported above and mortality rates of 0.135 (Austad) and
0.035 (Suter), the proportion of females surviving to deposit clutches one through
five would be 0.248, 0.045, 0.008, 0.001, and 0.0002 (Austad) and 0.710, 0.466,
0.305, 0.200, and 0.131 (Suter). An estimate of the expected relative contribution
of each clutch to lifetime fecundity can be derived from the product of the
survivorship probability and the expected number of live young (mean fertility X
mean clutch size). Those expected relative contributions, shown in Fig. 2, confirm
that longevity, particularly through the first two clutches, is crucial as a
determinant of lifetime fecundity in F pyramitela.

Size. — Prior to the present study, size variation in F pyramitela was already
known to be important in determining the outcomes of agonistic contests both
between males (Austad 1983; Suter and Keiley 1984) and between females (Hodge
1987). The data reported above indicate that mass also contributes directly to
fecundity per clutch (Table 1, Fig. 1), as it does in many other invertebrates. Thus
larger females of this species benefit because (1) their clutches are larger, (2) they
retain possession of their webs more frequently (Hodge 1987), (3) they capture
more prey biomass per unit time (Janetos 1983), and (4) they may have a
somewhat greater resistance to desiccation and other environmental challenges.
[The determinants of adult size in this species have not been explored but are
obviously important contributors to fitness. Presumably both size at hatching
(Suter and Parkhill 1990) and food availability, as well as genotype, are
involved.]

Foraging success. — Because nutrients are required to produce the yolk that is
the primary constituent of spider eggs, the positive relationship between feeding
rate and fecundity, and the negative relationship between feeding rate and latency
to oviposition, are expected. The relationships probably reflect reality under field

268

Figure 2. — The expected relative contribution to
lifetime fecundity of each clutch. The measure is
the product of the probability that the female will
survive to oviposit and the expected number of live
young (clutch fertility X clutch size) in the clutch,
all set relative to the first clutch (1.0). The filled
bars are based in part upon an estimate of female
mortality (0.035 /day) from Suter (1985); the open
bars are based upon an estimate of mortality
(0.135) dervied from Austad (1989).

Clutch Number

conditions: clutch sizes and latencies are comparable to those reported by Austad
(1989) and the feeding rates in the laboratory are representative of field
conditions (Austad 1989; Suter 1985). Both relationships confirm the findings of
Austad (1989) and indicate a positive contribution of foraging success to lifetime
fecundity. Because feeding rates in this study were not systematically
manipulated, however, the range of rates was relatively narrow. I propose to
explore the upper limits of food intake in this species to look for both clutch
mass and egg number constraints. Such a study would make possible a
comparison with the interesting report by Riechert and Tracy (1975) that there is
a limit to the number of eggs produced by the agelenid, Agelenopsis aperta
(Gertsch), but no limit to the total mass of eggs produced.

Janetos (1983) has shown that larger F. pyramitela capture larger prey, on
average, than do smaller ones. If this relationship holds for all sizes and instars,
then larger hatchlings (Suter and Parkhill 1990) would become among the largest
of adults and have all of the other advantages of large size to which I alluded
above. Clearly a female’s foraging success and her size reinforce each other in
ways that ultimately augment fecundity.

ACKNOWLEDGMENTS

I am very gratefully to Valerie Parkhill and Lauren Walberer, both
undergraduates at Vassar College, for their assistance in collecting and organizing
the data in this study. Their participation in the research was made possible by
funds from Vassar’s Undergraduate Research Summer Institute. David Wise and
an anonymous reviewer provided helpful comments on an earlier draft of the
manuscript.

LITERATURE CITED

Austad, S. N. 1982. First male sperm priority in the bowl and doily spider, Frontinella pyramitela
(Walckenaer). Evolution, 36:777-785.

Austad, S. N. 1983. A game theoretical interpretation of male combat in the bowl and doily spider
{Frontinella pyramitela). Anim. Behav., 31:59-73.

Austad, S. N. 1989. Life extension by dietary restriction in the bowl and doily spider, Frontinella
pyramitela. Exp. Gerontol., 24:83-92.

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269

Downes, M. F. 1988. The effect of temperature on oviposition interval and early development in
Theridion rufipes Lucas (Araneae, Theridiidae). J. Arachnol., 16:41-45.

Eberhard, W. G. 1979. Rates of egg production by tropical spiders in the field. Biotropica, 1 1:292-300.

Emlen, S. T. and P. W. Wrege. 1988. The role of kinship in helping decisions among white-fronted
bee-eaters. Behav. Ecol. Sociobiol., 23:305-315.

Endler, J. A. 1986. Natural Selection in the Wild. Princeton University Press, Princeton. 336 pp.

Fritz, R. S. and D. H. Morse. 1985. Reproductive success, growth rate and foraging decisions of the
crab spider Misumena vatia. Oecologia, 65:194-200.

Hodge, M. A. 1987. Agonistic interactions between female bowl and doily spiders (Araneae,
Linyphiidae): owner biased outcomes. J. Arachnol., 15:241-247.

Horn, H. S. and D. I. Rubenstein. 1984. Behavioural adaptations and life history. Pp. 279-298, In
Behavioural Ecology: an Evolutionary Approach. (J. R. Krebs and N. B. Davies, eds.). Sinauer
Associates, Sunderland, Massachusetts.

Janetos, A. C. 1983. Comparative ecology of two linyphiid spiders (Araneae, Linyphiidae). J.
Arachnol., 11:315-322.

Kessler, A. 1971. Relation between egg production and food consumption in species of the genus
Pardosa (Lycosidae, Araneae) under experimental conditions of food-abundance and food-
shortage. Oecologia, 8:93-109.

Killebrew, D. W. and N. B. Ford. 1985. Reproductive tactics and female body size in the green lynx
spider, Peucetia viridans (Araneae, Oxyopidae). J. Arachnol., 13:375-382.

Miyashita, K. 1987a. Development and egg sac production of Achaearanea tepidariorum (C. L. Koch)
(Araneae, Theridiidae) under long and short photoperiods. J. Arachnol., 15:51-58.

Miyashita, K. 1987b. Egg production of Achaearanea tepidariorum (C. L. Koch) (Araneae,
Theridiidae) in the field in Japan. J. Arachnol., 15:130-132.

Morse, D. H. and R. S. Fritz. 1987. The consequences of foraging for reproductive success. Pp. 443-
455, In Foraging Behavior. (A. C. Kamil, et al., eds.). Plenum Press, New York.

Pointing, P. J. 1965. Some factors influencing the orientation of the spider, Frontinella communis
(Hentz) in its web (Araneae: Linyphiidae). Can. Entomol., 97:69-78.

Riechert, S. E. and C. R. Tracy. 1975. Thermal balance and prey availability: bases for a model
relating web-site characteristics to spider reproductive success. Ecology, 56:265-285.

Suter, R. B. 1984. Web tension and gravity as cues in spider orientation. Behav. Ecol. Sociobiol.,
16:31-36.

Suter, R. B. 1985. Intersexual competition for food in the bowl and doily spider, Frontinella
pyramitela (Linyphiidae). J. Arachnol., 13:61-70.

Suter, R. B., G. Doyle and C. M. Shane. 1987. Oviposition site selection by Frontinella pyramitela
(Araneae, Linyphiidae). J. Arachnol., 15:349-354.

Suter, R. B. and M. Keiley. 1984. Agonistic interactions between male Frontinella pyramitela
(Araneae, Linyphiidae). Behav. Ecol. Sociobiol., 15:1-7.

Suter, R. B. and V. S. Parkhill 1990. Fitness consequences of prolonged copulation in the bowl and
doily spider. Behav. Ecol. Sociobiol., 26:369-373.

Turnbull, A. L. 1962. Quantitative studies of the food of Linyphia triangularis Clerck (Araneae:
Linyphiidae). Can. Entomol., 94:1233-1249.

Turnbull, A. L. 1973. Ecology of the true spiders (Araneomorphae). Ann. Rev. Entomol., 18:305-348.

Vehrencamp, S. L. and J. W. Bradbury. 1984. Mating systems and ecology. Pp. 251-278, In
Behavioural Ecology: an Evolutionary Approach. (J. R. Krebs and N. B. Davies, eds.). Sinauer
Associates, Sunderland, Massachusetts.

Wise, D. H. 1979. Effects of an experimental increase in prey abundance upon the reproductive rates
of two orb-weaving spider species (Araneae: Araneidae). Oecologia, 41:289-300.

Manuscript received November 1989, revised March 1990.

3 «? '

Smith, G. T. 1990. Potential lifetime fecundity and the factors affecting annual fecundity in Urodacus
armatus (Scorpiones, Scorpionidae). J. Arachnol., 18:271-280.

POTENTIAL LIFETIME FECUNDITY
AND THE FACTORS AFFECTING ANNUAL FECUNDITY
IN URODACUS ARMATUS (SCORPIONES, SCORPIONIDAE)

G. T. Smith

CSIRO Division of Wildlife and Ecology
LMB 4 PO Midland
Western Australia 6056 Australia

ABSTRACT

The ovariuterus of Urodacus armatus had three types of diverticula, Rudimentary (RD), Embryonic
(ED) and Post Partum (PPD). The data suggested that all the ova were developed and enclosed in
RDs by the time a female reached maturity and that the sum of the diverticula gave a measure of the
potential lifetime fecundity. Samples from two populations in two consecutive years were not
significantly different and the combined mean for all diverticula was 56.7 ± 8.22.

Annual fecundity (number of EDs) did not differ between populations or years and the combined
mean was 8.3 (range 4-12). Fecundity was not significantly influenced by female condition
(3 \JM ass / carapace length), length of ovariuterus or the total number of diverticula. However, size and
age had significant effects. The simplest adequate model explaining the variation was given by the
equation log ED = 0.9656 — 0.07003 Age + 0.01839 Carapace length. Data on age-related fecundity
and total diverticula suggested that females may have from 5 to 12 litters in a lifetime.

INTRODUCTION

Studies on a variety of invertebrates have shown that fecundity can be
influenced by a number of variables: size, (Juliano 1985; King 1987; Banks and
Thompson 1987; Haack et al. 1987); population density, (Wise 1975; Banks and
Thompson 1987); food, (Wise 1975; Riechert and Tracey 1975; Haack et al. 1987);
age, (Ribi and Gebhardt 1986); temperature, (Baird et al. 1987); geographic
location, (Hines 1982; Davies 1987; Atkinson and Begon 1987; Ribi and Gebhardt

1986) ; size of egg or offspring, (Ribi and Gebhardt 1986); size of male ejaculate,
(Svard and Wiklund 1988); number of previous matings by male, (Rutowski et al.

1987) , and clutch interval, (Banks and Thompson 1987). The variables that affect
fecundity in individual species differ as do the direction of the effect and the
degree of interaction with one another. Size, for most species, is the dominant
variable either directly or indirectly via its effect on other variables affecting
fecundity. Lifetime fecundity or reproductive success has been studied in only a
few species (Banks and Thompson 1987; Fincke 1987; Koenig and Albano 1987;
Svard and Wiklund 1988). In addition to the variables that affect individual
breeding events, lifetime fecundity will be affected by the length of reproductive
life, number of clutches and variables associated with the male. The majority of
the above studies are on short-lived, oviparous species; there have been no studies
on long-lived viviparous invertebrates.

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THE JOURNAL OF ARACHNOLOGY

Most data on reproductive rates in scorpions are measures of fertility (number
of live births) obtained from specimens in capativity or animals in the field (Polis
and Farley 1979), and both methods may give values less than the true
reproductive rate. Captive specimens, depending on the time spent incaptivity
may have more abortions, suffer from maternal cannibalism or displacement of
young from the mother’s back and may fail to shed the birth membrane (Polis
and Farley 1979). Similar mortality factors also operate on litters in the field but
have not been directly observed (Smith 1966; Polis and Farley 1979).

In viviparous animals, such as scorpions, no methods have been developed to
attain data on fecundity (number of fertilized ova) without sacrificing the animal.
However, in detailed studies on population dynamics and life history strategies, it
is important to have a measure of maternal investment in reproduction and the
extent of pre-parturition mortality. Given that fertility (litter size) will be
dependent on the fecundity, it is important to have an understanding of the
factors affecting fecundity, so that these can be applied to data from a given
population.

Fecundity has been calculated for only a few scorpions (Smith 1966; Polis and
Farley 1979); individual and intraspecific variability and the factors influencing
this variability have not been studied. This paper examines the potential lifetime
fecundity and the factors affecting annual fecundity in the burrowing scorpion
Urodacus armatus Pocock. U. armatus is a burrowing species widely distributed
over arid and semi-arid Australia with no apparent habitat restrictions in terms of
soil type or vegetation. Scorpion activity, as measured by the number of active
burrows, is greatest in the period March to May (= Fall) with a smaller peak
from September to October (= Spring). Parturition starts in February and the
second instars disperse from their natal burrows in March and April. The
gestation period is about 1 1 months.

MATERIALS AND METHODS

The study site was Durokoppin Nature Reserve (1030 ha), 150 km northeast of
Perth, Western Australia. The reserve had a mosaic of heath, shrub and
woodland communities. U. armatus , a medium sized (total length 75 mm)
burrowing species was found throughout the reserve, but was most abundant in
woodland patches where there were 1000-3000/ ha (Smith unpublished data).

Samples of pregnant female U, armatus were collected from two woodland
patches in September and October of 1985 and 1986 and in one patch, a further
sample was collected in March 1986, giving a total of 198 females. Females were
collected by placing pitfall traps (plastic drinking cups) in front of the burrows.
The traps were visited at sunrise in the following days and any scorpions were
removed and kept cool until they were weighed to the nearest 0.01 g that evening.
They were then killed by heat shock and preserved in 70% ethanol.

In the laboratory, the length of the carapace, right chela and tail were
measured to the nearest 0.01 mm and the specimen dissected to expose the
ovariuterus. Attached to the ovariuterus were three types of diverticula (Fig. 1) as
described for U . manicatus (Thorell) (as V. abruptus , Smith 1966), Rudimentary
diverticula [(RD), small finger-like projections with the ovum at the distal end,
with three distinct size classes]; Embryonic diverticula [(ED), large projections

SMITH-FECUNDITY IN URODACUS ARMATUS

273

To genital opening

t \

Figure 1. — Ventral view of the ovariuterus of U. armatus showing arrangement of Rudimentary
diverticula (1) showing the three size classes. Embryonic diverticula (2) and one Post-Partum
diverticulum (3) to indicate shape and size.

with a distinctive knob at the distal end and which contain the developing
embryo] and Post Patrum diverticula [(PPD, small, squat infolded structures that
are formed from the sheath of the EDs when the young are born]. The numbers
of each type of diverticula were counted and the length of the network of the
ovariuterus (OUL) was measured to the nearest 0.1 mm from the first proximal
bifurcation on the lateral branches. The numbers of in utero deaths (= abortions)
in both the current and previous pregnancies were recorded. Abortions in the
current pregnancy had EDs that were shorter and thinner while abortions from
previous pregnancies were distinguished by the diverticula being very short, thin
and dark.

_ The relative age of adult females was calculated from the formula: No. PPD/
XED + 1. Assuming that if the numbers of PPDs were equal to or less than the

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maximum number of EDs (from all samples), then they represented the first
pregnancy for that individual. Knowing the mean number and range of embryos
in the first and second pregnancies, the relative age of females that had had more
than two pregnancies was recalculated. This procedure was repeated a number of
times to produce Table 1, which was used to assign age classes to individuals.
Clearly, for the individual, the method was accurate only for females in their first
and, to a lesser extent, in their second pregnancy. For later pregnancies, the
accuracy was unknown, but for large samples, the errors should have cancelled
out each other. In this scheme, relative age was related to the number of
pregnancies; its relationship to chronological age was uncertain because not all
females bred every year (the number of females that did not breed is indicated by
the difference in the sample sizes for ED and CL in the first four samples in
Table 3) and the age at maturity was not known with certainty. Log-log plots of
carapace length against length of the right chela did not give distinct clumps but
suggested that adults were in their sixth instar. Using the theoretical method of
Francke and Sissom (1984) to calculate the number of molts between the second
instar and the adults also suggested that adults were in their sixth instar (Smith
unpublished data). Second instar U. armatus remained in that stadium for about
12 months and assuming that later stadia were of similar duration, then females
mating after their final molt were in their fifth year. For convenience, relative age
or number of pregnancies will be called simply age in the following discussion.

In analyzing the data, the length of the carapace was used as a measure of size
(CL) and the condition (C) of the female was calculated from the formula C =
mass/CL.

Females were collected in September and October to take advantage of the
increased activity at this time and to ensure that the EDs had developed to a
stage where they could not be confused with RDs.

RESULTS

Potential lifetime fecundity. — Examination of the samples from September and
October showed that the ovariuterus in an immature female was a thin tube with
no diverticula. In the fifth and possibly fourth instar, it had a number of small
dense patches that may be sites of the developing ova and diverticula. By autumn,
after the final molt, the ovariuterus was fully developed with RDs of three
distinct size classes (Fig. 1). Presumably the ovariuterus of a fifth instar female
finished its final development shortly before or at about the time of the final
molt.

Initial inspection of the data suggested that a female’s lifetime complement of
ova were formed by the time she reached adult size, and that the sum of three
types of diverticula were a measure of the potential lifetime fecundity, assuming
that the PPDs were not resorbed.

This idea was tested with the present data in two ways. Firstly, in the March
1986 sample, the total number of diverticula in virgin females and those who were
in their first pregnancy, should not differ significantly from those in their second
or later pregnancies. The respective means, 51.7 and 55.5, were not significantly
different (t = 1 .62, df= 23, P > 0.05).

Secondly, the number of RDs should decline with age while the total number
of diverticula (TD) should not differ significantly with age. The number of RDs

SMITH— FECUNDITY IN URODACUS ARMATUS

275

Table I. The calculated means of Embryonic diverticula (ED) and Post-Partum diverticula (PPD)
with the range of PPDs for female U. armatus which have had 1 to 8 pregnancies.

No.

Mean

Range

pregnancies

PPD

< 12

13-21

22-28

29-35

36-42

43-48

49-55

showed a steady decline from 44.5 at age one to 17.8 at age six (Table 2). One six
year old had no RDs and the one seven and one eight year old had 20 and 8 RDs
respectively. While the decrease from one age to another was less than expected
from the number of embryos for different ages shown in Table 1, the true extent
of the decline was masked by the variability in the numbers of TDs. A better
indication of the progressive use of RDs with age was the mean percentage of TD
that were still RDs (Table 2). This percentage fell from 82.6% at age one to 20.0%
at age six which agreed well with the expected decline when it was calculated
from the mean number of TDs and the annual fecundity with age given in Table
1 (Table 2).

The mean number of TD increased from 53.8 at age one to 62.7 for the
combined five to eight age group (Table 2) and there was a significant difference
with age (ANOVA F — 6.38, df 4, 186, P < 0.01). The mean number of TDs in
the five to eight year olds was significantly greater than the mean TDs for one
and two year olds, three and four year olds also had significantly larger mean
TDs than one year olds (Newman-Keuls test, P < 0.05). The relationship between
TD and the age, size (CL) and size of ovariaterus (OUL) of females was analyzed
using multiple regression with a log transformation of the data from 186 females.
Age had no significant effect on TD, while CL and OUL has significant positive
effects, the variance ratios were 24.15 (P < 0.001) and 29.15 (P < 0.001)
respectively. The relationship was expressed by the equation:

log TD = 2.651 + 0.01282 CL + 0.001517 OUL.

Table 2. — Mean and standard deviation (SD) at different ages of the number of rudimentary
diverticula (RD), the mean percentage of RDs (RD X 100/TD), the calculated percentage of RDs
(Calc % RD) using the average number of diverticula and the age related fecundity (Table 1) and the
mean and standard deviation of the total number of diverticula (TD) in female U. armatus. * = mean
and standard deviation from combined five to eight year old females.

Age

Mean

RD X 100/TD
Mean SD

Calc

%RD

Mean

Sample

size

44.5

6.9

82.6

3.2

53.8

7.4

39.0

6.5

68.8

5.0

56.2

9.4

34.7

6.8

57.5

5.4

59.5

8.0

26.5

4.9

44.4

4.0

59.1

5.0

20.5

8.9

57.5

12.3

62.1*

6.1*

17.8

9.0

20.0

15.7

—

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THE JOURNAL OF ARACHNOLOGY

These data show that the increase in TDs with age was related to the increase in
CL and OUL with age (survivorship increases with size) rather than the
development of new RDs.

Annual fecundity. — The mean, standard deviation and range for fecundity and
five factors that may affect fecundity are given for each sample in Table 3.

Overall annual fecundity ranged from 4 to 12 with a mean of 8. Initial
inspection of the above factors suggested that all exerted some effect. The data
were then analyzed using an analysis of covariance with a log transformation
using the GLIM program (Baker and Nelder 1977). In the sample of 198, the data
from 29 females which were not pregnant were deleted for the first analysis. The
analysis showed no significant difference between the samples (variance ratios
from —0.3883 to 2.127) and the data from the samples were combined. The effect
of four factors (Carapace length, age, condition and TD) on fecundity were then
analyzed. TD, with a variance ratio of 0.8367, was insignificant and was dropped.
Condition, with a variance ratio of 2.239, also not significant, was dropped,
leaving age and size as the only significant factors with variance ratios of 6.407
and 5.455 respectively. The analysis was repeated with ovariuterus length (OUL)
but excluding TD and excluding 1 1 females for whom data of ovariuterus length
were not available. OUL was not significant (variance ratio 0.5191), leaving age
and size again as the only significant factors affecting fecundity with variance
ratios of 7.125 and 5.068 respectively.

The simplest adequate model explaining variation in fecundity was given by the
formula:

log ED = 0.9656 - 0.07003 Age + 0.01839 CL

The realized reproductive potential or the number of live births (fertility) is not
necessarily the same as the fecundity because of the possibility of abortions. Of
the 198 females examined, 70 had had abortions; only 4 of these were in EDs (1,
2, 2, 3). This suggested that most abortions that were recognized were in the
latter half of the gestation period. Overall, the mean number of abortions per
pregnancy was 0.8. In 17 age-two females, 12 had only one abortion, 3 had two
abortions and one each had 5 and 6 abortions. Data from older females suggested
that this was reasonable indication of the range of the numbers of abortions per
pregnancy, based on the average number per pregnancy.

Number of pregnancies. — Females with the mean number of TDs and average
fecundity (Table 1) could have eight pregnancies, however, females with TDs at
the extremes of the range (34 to 80) could have from 5 to 12 pregnancies.
Examination of the number of RDs in 4, 5 and 6 year old females showed that
the potential number of pregnancies that they could have ranged from 7 to 11, 7
to 11 and 6 to 10 respectively. The two 7-year olds could have had another three
pregnancies while the one 8-year old could have had one more pregnancy.
Clearly, few, if any females, survive long enough to realize their full reproductive
potential

DISCUSSION

The true measure of fecundity is the number of fertilized ova; however, this is
not an easy measure to obtain and is probably not important in the population
dynamics of U. armatus given the limited provisioning required at this stage of

SMITH — FECUNDITY IN URODACUS ARMATUS

277

Table 3. — Mean (X), standard deviation (SD), range (rg) and sample size (N) of the number of
embryonic diverticula (ED), total number of diverticula (TD), carapace length (CL), condition (C),
Age (A) and length of ovariuterus (OUL) in female U. armatus. Note that sample sizes vary within a
sample because some females were not pregnant or the data for some factors were not available.

Sample

OUL

Area 1

7.7

58.8

6.87

0.145

2.7

321.9

1985

1.67

9.22

0.34

0.006

1.40

38.11

4-12

44-80

6. 2-7. 4

0.128-0.157

1-8

249-434

Area 1

8.8

54.9

7.05

0.145

2.2

306.2

1986

1.86

8.20

0.35

0.008

1.46

32.46

4-12

34-76

6.4-7. 7

0.122-0.167

1-7

248-390

Area 2

8.7

59.6

7.43

0.141

2.3

327.3

1985

1.73

6.76

0.29

0.006

1.34

50.82

5-11

40-71

6.9-8. 1

0.120-0.152

1-7

267-430

Area 2

8.4

57.2

7.08

0.142

2.6

303.7

1986

1.25

7.33

0.38

0.008

1.41

32.20

6-11

45-72

6. 1-7.9

0.111-0.157

1-6

249-364

Area 2

8.3

53.8

7.17

2.2

286.3

March

1.34

6.39

0.39

—

1.35

22.55

1986

6-11

47-65

6.5-8. 1

1-6

250-350

—

262

development. Fecundity in this study was calculated at about halfway through the
gestation period and was not significantly different from that obtained shortly
after mating. It is therefore the best time to collect samples as it takes advantage
of the increased activity and avoids any confusion in the identification of RDs
and EDs. Further, the data suggest that most abortions probably occur in the
second half of the gestation period.

Mean fecundity for the study was 8.3, which was considerably smaller than the
mean fertility of 31.3 calculated by Polis and Farley (1979) from data on 39
species. More recently, Polis and Sissom (1990) have provided data from 77
species on litter sizes, which ranged from one to 105, with a mean of 25; only 11
species had litter sizes comparable to the fecundity of U. armatus. The data were
not detailed enough to make statistical comparisons, however, from the data
available it is clear that fecundity in U. armatus and its variability (CV for the 5
samples range from 14.9% to 21.8%) is among the lowest found in scorpions.

The only comparable study is that of Smith (1966), who calculated that
fecundity in U. manicatus (a slightly smaller species, CL -- 5.7 mm) to be 15.7
with 4.5% of embryos being aborted. The litter size of females in the field was
1 1.4, indicating a 24% mortality in immediate post-birth period.

The factors influencing variation in fecundity were examined; size had a
significant positive effect while age had a significance negative effect. Other
factors (condition, length of ovariuterus and total number of diverticula) had
positive but not significant effects. Size and age affect intraspecific fecundity in

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THE JOURNAL OF ARACHNOLOGY

both invertebrates (see Introduction for references) and vertebrates (Allaine et al.
1987; Sauer and Slade 1987). In invertebrates, size is commonly a positive factor,
but in some species or situations, it may be neutral or negative in its effect
(Haack et al. 1987). Similar effects are seen in relation to age (Davies 1987; Ribi
and Gebhardt 1986). Francke (1981) showed that female size (CL) and the size of
second instar young (CL) accounted for 81% of the variability in litter size in an
interspecific study of diplocentrid scorpions. Bradley (1984) found that adult size
(CL) in Paruroctonus utahensis Williams was not related to brood size (second
instar) or the weight of the young. There are no data on the relationships between
fecundity and size of young in U. armatus , however in U. manicatus there was no
significant relationship between female size (CL) and the size (CL) of either first
or second instars (Smith, unpublished data).

Female condition reflects the amount of food stored in the hepato-pancreatic
gland and indirectly, the females foraging efficiency and/or success. For most
females collected in spring, just after reopening their burrows, condition should
reflect the foraging success in autumn at mating and it might be expected that
variations in condition would be reflected in the fecundity as is found in other
arachnids (Wise 1975). The lack of a significant effect is similar to Bradley’s
(1984) finding that feeding rates do not effect brood size nor the size of the young
(second instars) in P. utahensis. Also, Polis (1988) found that in P. mesaensis
Stahnke, high levels of food intake increased the rate of development but not the
fecundity. On the other hand, starvation eventually led to the resorption of the
embryos. Similar observations have been made on various Urodacus species
(Smith, unpublished data). Metabolic rates in scorpions are very low (Hadley and
Hill 1969; Riddle 1978) and it is likely that energy requirements for the
embryonic development in the first half of the gestation period are also low. If
the energy requirements of pregnant female U. armatus are similar to those of P.
utahensis and P. maesensis , then food would not be a limiting factor for U.
armatus , except under the most severe conditions. Under average conditions,
reproductive potential is strongly influenced by the size and age of the
population. Size itself may be influenced also by the individual’s rate of
development.

Studies on female lifetime reproductive success in invertebrates appear to be
limited to a few studies on Odonata (Fincke 1987; Banks and Thompson 1987;
Koenig and Albano 1987) and the monarch butterfly (Svard and Wiklund 1988)
and are not comparable with a viviparous iteroparous invertebrate, with
determinate lifetime fecundity. Perhaps a better comparison is with mammals,
where oogenesis and follicular formation is completed at about parturition.
However, in mammals, the number of follicles far exceeds those required even
under the most favorable breeding conditions (Gosden and Telfer 1987).

In this study, I have used morphological characteristics of the ovariuterus and
its diverticula to demonstrate that all the ova are developed and enclosed in
rudimentary diverticula around the time the female molts into her last instar and
that the ova are progressively used over the lifetime of the female. A study of U.
manicatus showed a similar relationship between the numbers of the different
types of diverticula with age. Further, limited histological examination of the
ovariuterus of females of different age showed no evidence of new ova being
developed after the females had completed their final molt. Examination of a
limited number (1-20) of 5 other species of Urodacus suggests that all Urodacus

SMITH FECUNDITY IN URODACUS ARMATUS

279

may have a similar reproductive strategy and further, that this strategy may be
common to all scorpions with katoikogenic development (Scorpionidae and
Diplocentridae).

The reproductive strategy of U. armatus is one of long life, delayed maturity
and low potential lifetime fecundity and annual fecundity; traits that have
probably coevolved with the habit of burrowing and foraging from the burrow
entrance; both will increase survivorship. The most vulnerable period for U.
armatus is when the second instar individuals are dispersing from their natal
burrows as was found for U. manicatus (Smith 1966). Once the second instars
have dug their own burrows, survivorship is probably high and hence there is no
need for a high reproductive rate. These adaptations are characteristic of
equilibrium species and are typical of a number of scorpion species that create
their own stable and predictable environment by constructing burrows (Polis and
Farley 1980). Further these adaptations may be viewed as a refinement of those
that led to the development of the extremely low metabolic rate which appear to
be characteristic of all scorpions (Polis 1988).

ACKNOWLEDGMENTS

I would like to thank Jana Ross for her help in collecting the scorpions and for
carrying out the dissections, Richard Litchfield for statistical advice and for
running the GLIM program, and Perry de Rebeira for the drawing. Eleanor
Rowley, Denis Saunders, James RidsdilLSmith, Gary Polis, and David Sissom
made valuable comments on various drafts, which Claire Taplin typed.

LITERATURE CITED

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relationship between fecundity and adult body weight in homeotherms. Oecologia, 73:478-480.

Atkinson, D. and M. Begon. 1987. Reproductive variation and adult size in two co-occurring
grasshopper species. Ecol. EntomoL, 12:119-127.

Baird, D. J., L. R. Linton and R. W. Davies. 1987. Life history flexibility as a strategy for survival in
a variable environment. Funct. Ecoh, 1:45-48.

Baker, R. J. and J. A. Nelder. 1977. The GLIM system manual, release 3. Numerical Algorithms
Group, Oxford.

Banks, M. J. and D. J. Thompson. 1987. Lifetime reproductive success of females of the damselfly
Coenargrion puella. J. Anim. Ecol., 56:815-832.

Bradley, R. A. 1984. The influence of the quantity of food on fecundity in the desert grassland
scorpion ( Paruroctonus utahensis) (Scorpionida: Vaejovidae): An experimental test. Oecologia,
62:53-56.

Davies, L. 1987. Long adult life, low reproduction and competition in two sub-Antarctic carabid
beetles. Ecol. Entomol. 12:149-162.

Fincke, O. M. 1987. Lifetime reproductive success and the opportunity for selection in a non-
territorial damselfly (Odonata: Coenagrionidae). Evolution, 40:791-803.

Francke, O. F. 1981. Birth behavior and life history of Diplocentrus spitzeri Stahnke (Scorpiones:
Diplocentridae). Southwest. Natu., 25:517-523.

Francke, O. F. and W. D. Sissom. 1984. Comparative review of the methods used to determine the
number of molts to maturity in scorpions (Arachnida), with analysis of the post-birth development
of Vaejovis coahuilae Williams (Vaejovidae). J. Arachnol., 12:1-20.

Gosden, R. G. and E. Telfer. 1987. Numbers of follicles and oocytes in mammalian ovaries and their
allometric relationships. J. Zook, Lond., 21 1:169-175.

Haack, R. A., R. C. Wilkinson and J. L. Foltz. 1987. Plasticity in life history traits of the bark beetle
Ips calligraphus as influenced by phloem thickness. Oecologia, 72:32-38.

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Hadley, N. F. and R. D. Hill. 1969. Oxygen consumption of the scorpion Centruroides sculpturatus.
Comp. Biochem. Physiol., 29:217-226.

Hines, A. H. 1982. Allometric constraints and variables of reproductive effort in Brachyuran crabs.
Marine Biol., 69:309-320.

Juliano, S. A. 1985. The effects of body size on mating and reproduction in Brachinus lateralis
(Coleoptera: Carabidae). Ecol. Entomol., 10:271-280.

King, G. H. 1987. Offspring sex ratios in parasitoid wasps. Quart. Rev. Biol., 62:367-396.

Koenig, W. D. and S. S. Albano. 1987. Lifetime reproductive success, selection, and the opportunity
for selection in the white-tailed skimmer Plathemis lydia (Odonata: Libellulidae). Evolution, 41:22-36.

Polis, G. A. 1988. Foraging and evolutionary responses of desert scorpions to harsh environmental
periods of food stress. J. of Arid Environ., 14:123-134.

Polis, G. A. and R. D. Farley. 1979. Characteristics and environmental determinants of natality,
growth and maturity in a natural population of the desert scorpion. Paruroctonus mesaensis
(Scorpionida: Vaejovidae). J. Zool., Lond., 187:517-542.

Polis, G. A. and R. D. Farley. 1980. Population biology of a desert scorpion: survivorship,
microhabitat and the evolution of life history strategy. Ecology, 61:620-629.

Polis, G. A. and W. D. Sissom. 1990. Life history. Pp. 161-223, In Biology of Scorpions. (G. A. Polis,
ed.) Stanford University Press. Stanford.

Ribi, G. and M. Gebhardt. 1986. Age specific fecundity and size of offspring in the prosobranch snail
Viviparus ater. Oecologia (Berlin), 71:18-24.

Riddle, W. A. 1978. Respiratory physiology of the desert grassland scorpion Paruroctonus utahensis.
J. Arid Environ., 1:243-251.

Riechert, S. E. and C. R. Tracey. 1975. Thermal balance and prey availability: bases for a model
relating web-site characteristics to spider reproductive success. Ecology, 56:265-285.

Rutowski, R. L., G. W. Gilchrist and B. Terkanian. 1987. Female butterflies mated with recently
mated males show reduced reproductive output. Behav. Ecol. Sociobiol, 20:319-322.

Sauer, J. R. and N. A. Slade. 1987. Uinta ground squirrel demography: is body mass a better
categorical variable than age? Ecology, 68:642-650.

Smith, G. T. 1966. Observations on the life history of the scorpion Urodacus armatus Pocock
(Scorpionidae), and an analysis of its home sites. Aust. J. Zool., 14:383-398.

Svard, L. and C. Wiklund. 1988. Fecundity, egg weight and longevity in relation to multiple matings
in females of the monarch butterfly. Behav. Ecol. Sociobiol., 23:39-43.

Wise, D. H. 1975. Food limitation of the spider Linyphia marginata: experimental field studies.
Ecology, 56:637-646.

Manuscript received July 1989, revised March 1990.

Coyle, F. A. and T. C. O’Shields. 1990. Courtship and mating behavior of Thelochoris harsh
(Araneae, Dipluridae), an African funnel web spider. J. Arachnol., 18:281-296.

COURTSHIP AND MATING BEHAVIOR OF
THELECHORIS KARSCHI (ARANEAE, DIPLURIDAE),
AN AFRICAN FUNNELWEB SPIDER

Frederick A. Coyle and Theresa C. O’Shields

Department of Biology
Western Carolina University

Cullowhee, North Carolina 28723 USA

ABSTRACT

The courtship of Thelechoris karschi , an African funnelweb mygalomorph spider, consists of an

early non-contact phase of vibratory signaling and then a contact phase involving leg-fencing and,
sometimes, lunging. Eventually the male clasps the female’s pedipalps with his first tibial apophyses,
tilts her upwards and backwards, and attempts to insert his palpal organs alternately. There was much
variation among successful courtships in the amount of aggression (lunging and chasing). Mating was
characterized by numerous bouts of unsuccessful palpal insertation attempts, relatively few successful
insertations, and a tendency for repeated courtships and copulations. It is pointed out that ample
opportunity for sexual selection by female choice exists during these courtships and copulation
attempts, and that the lengthy and repeated copulations may be, in part, a consequence of genital
anatomy.

INTRODUCTION

Thelechoris karschi Bdsenberg and Lenz is a moderately large dip lurid spider

(adult body length 11-20 cm) with extremely long lateral spinnerets which are
used to build conspicuous, perennial capture webs. The webs consist of a large
(up to 1500 cm2 viewed from above), three-dimensional, exposed capture area of
interconnected sheets and passageways funneling into a protected tubular silk
retreat, and are located in a wide variety of microhabitats, from rock piles and
road banks to tree trunks and shrubs. This species is quite common in some
localities and occurs in a wide variety of arid to mesic habitats (except for
extreme habitats like desert and wet forest) over a large part of eastern and
south-central Africa, from Kenya southwest to Namibia.

Of the 18 currently recognized genera of Dipluridae (Raven 1985; Coyle 1986a),
observations of courtship and/or mating have been published for only four:
Microhexura (Coyle 1985), Euagrus (Coyle 1986b), Australothele (Raven 1988),
and Phyxioschema (Raven and Schwendinger 1989). The observations presented
herein on the courtship and mating of Thelechoris karschi are the first for this
genus and its subfamily (Ischnothelinae). A similar study of reproductive behavior
in the other two ischnotheline genera ( Ischnothele and Lathrothele) is currently
being conducted by the first author.

Our primary objective in this study was to carefully describe the courtship and
mating behavior of T karschi to obtain behavioral characters for eventual use in

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testing phylogenies. Secondary objectives were 1) to begin testing the hypothesis
that the T karschi populations we have been studying are not behaviorally
isolated from one another and 2) to propose hypotheses about the functional
significance and origins of some of the behaviors observed. We hope this paper
will be a stimulus and a useful foundation for future studies.

MATERIALS AND METHODS

Although the spiders used in this study were collected from the following eight
localities in three different areas of East Africa, a preliminary analysis of
morphological variation suggests that they ail belong to one species, T karschi .
The four populations (A-D) from the coast of eastern Kenya are about 130 miles
east of population E in Tsavo West National Park in the interior of Kenya. Both
of these sets of populations are about 900 miles north of the three populations
(F-H) in southern Malawi.

Coastal Kenya: population A - Kilifi and 9 km N Kilifi, 10-50 m elev., old field
with scattered trees, shrubs, and hedgerow, 27-29 March 1989; population B -
Jimba, 3 km SE Gedi, 100 m elev., second growth forest, 28 March 1989;
population C - Shimba Hills Natural Reserve, S Kwale, 330 m elev., camping
area in forest patch, 31 March 1989; population D - Shelly Beach Road, few km
S Mombasa, 30 m elev., old field with scattered trees, 1 April 1989. Interior
Kenya: population E - Tsavo West National Park, Kitani Lodge, 41 km S Mitito
Andei, 750 m elev., rock garden, 15 April 1989. Malawi: population F - along
Likhubula River at base of Mulanje Mountain, 750-850 m elev., 18 April 1989;
population G - 24-26 km N Zomba on route Ml, 750 m elev., road bank, 21-22
April 1989; population H - Blantyre, 1000 m elev., yard and garden, 22 April
1989.

In the laboratory each adult male was kept in a clear plastic drinking cup
covered with a petri dish lid and nested in an identical cup. A pad of moist
cotton between the bottoms of the two cups provided moisture through a hole
punched in the bottom of the inner cup. The 17 females used in the study were
large (therefore presumably mature) and were active silk-spinners. Each of these
constructed a web in an observation arena. One type of arena was a clear plastic
shoe box (29 X 15 X 8.5 cm high) with construction paper covering its floor.
Either a clear vial was taped to the floor at one end to serve as a retreat or the
female was allowed to construct her retreat and capture web in any part of the
arena. These webs were misted with water every other day. The other type of
arena, resembling an “ant farm” container, allowed for especially close
observation of courtship and mating without unduly restricting the participants.
It consisted of two panes of glass (15 X 24 cm) separated by a 1. 5-3.0 cm thick
U-shaped wooden frame mounted upright on a wooden base. The female
constructed her web between the panes of glass, a piece of styrofoam plugged the
opening at the top of the frame, and water was periodically added to a wet cotton
ball in the bottom of the arena. The spiders were maintained at 24° C and a 12-
hour photoperiod. They were fed a mealworm ( Tenebrio ) larva approximately
once every ten days, and rarely a cricket nymph or a few house flies.

Male-female encounters were initiated by gently dropping the male onto the
female web far from her retreat. All encounters occurred between 6 May and 30
June (39 encounters) and 19 and 27 September (six encounters) 1989 during the

COYLE & O’SHIELDS— MATING BEHAVIOR OF THELECHORIS KARSCHI

283

daylight period (primarily afternoon hours). Most encounters were recorded with
a Panasonic WV-D5000 video recorder equipped with a Micro-Nikkor 55 mm
close-up lens. The arenas were lighted from above by fluorescent ceiling lights
and a fluorescent desk lamp and sometimes also from the front by a 75 watt
incandescent bulb. Actions that were not being recorded through the lens were
often recorded verbally on the audio channel of the recorder. Behaviors were
analyzed with slow-motion and single frame advance modes (which allowed one
second of action to be subdivided into 30 individual stop-action frames).

The spermathecae of 15 T. karschi females from several localities in East Africa
were removed, cleared in 85% lactic acid, and examined and measured with a
compound light microscope at 40X and 100X. The location of sperm and semen
(recognized by their granular translucence) was recorded. Some spermathecae
were drawn with the aid of a drawing tube. The palpal emboli of twelve males
from the same localities were measured at 100X with a stereomicroscope.

RESULTS

Adult males were moderately common in populations A and C when sampled
in late March, just before the onset of the rainy season (late March through
May), and were very common (although still seemingly much less abundant than
adult females) in population E in mid April, during the rainy season. No adult
males were found in populations F, G, and H when they were sampled in late
April, after the end of the rainy season (November to April) in southern Malawi.
While some adult males were apparently in their own webs, others were in webs
with females.

Table 1 summarizes outcomes of the 45 male-female encounters. Ninety percent
of all courtships were initiated by the male. Eight of the 16 unsuccessful
courtships (those that failed to progress to a copulation attempt) involved non-
receptive females which did not perform any courtship signals, one involved an
apparently unreceptive male that was briefly courted by the female, and the other
seven involved reciprocal courting. In eight of the 14 encounters that led to
copulation attempts (A, A, or X in Table 1) (a copulation attempt was defined as
all the palpal insertion attempts occurring between the onset of clasping and the
subsequent uncoupling event) there were multiple attempts, giving a total of 28
copulation attempts (and thus 28 “successful” courtships) during this study. Only
two of the 13 encounters among spiders from coastal Kenyan populations led to
mutual courtship, and neither of these led to a copulation attempt. Five of the 14
encounters initiated among population E spiders resulted in successful copulations
(X in Table 1) (a copulation was judged successful if at any time the embolus was
observed to be fully inserted and palpal flexions moved the female’s abdomen; no
additional effort was made to determine whether insemination actually occurred).
Six successful copulations occurred between individuals from distant populations.
Females Ell and E28 and males E3 and E6 each copulated successfully with
more than one individual.

Since we have little or no information about the reproductive history of the 21
females used in this study, and since at least some of them had mated before they
were collected (four that did not attempt copulation deposited fertile eggs),
correlations between observed reproductive success and observed mating behavior
are meaningless.

Table h — Outcomes of laboratory encounters of male and female Thelechoris karschi. Specimen code letters identify populations as described in
Methods section. Outcomes indicated by following symbols: O = no courtship behavior; M — male courts briefly; F = female courts briefly; MF = both
individuals court, but do not attempt copulation; A = copulation attempted (palpal insertions attempted), but no palpal insertions (A) or uncertain
whether insertions occurred (A); X = copulation with palpal insertions. Multiple A’s and/or X’s indicate multiple copulation attempts in a single
encounter. Repeat encounters of same individuals are separated by commas. Asterisks designate encounters that were ended by female attacks.

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THE JOURNAL OF ARACHNOLOGY

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COYLE & O’SHIELDS— MATING BEHAVIOR OF THELECHORIS KARSCHI

285

Ten (22%) of the encounters were ended by clearly life-threatening attacks by
the female (Table 1). Five of these were interrupted early (we removed the male
before he was injured) and five (that were not interrupted as quickly) resulted in
serious injury to the male, i.e., severed legs (three attacks), a broken leg (one
attack), and a severed spinneret (one attack). Six of the attacks occurred early in
the encounter, either before any courtship behavior (two attacks) or while the
male was courting non-courting females (four attacks). Although three of the
other four attacks occurred either after a failed attempt at clasping (one attack)
or after copulation attempts (two attacks), none occurred immediately after
uncoupling; the fourth attack occurred several minutes after uncoupling as the
male moved about the web in the confines of the observation arena.

Behavioral units. — The following section describes each of the behavioral units
which collectively comprise T. karschi courtship and mating behavior.

Advance: forward movement which brings one spider closer to the other. Often
an advance is an ambulatory advance involving the displacement of all tarsi, but
some advances consist only of a shifting forward of the anterior legs or body.
Advances may be accompanied by other behavioral units (quivering, twitching,
jerking, and tapping). Lunges and chases are special aggressive advances.

Lunge : sudden vigorous forward and/or downward thrust of the body toward
the other spider with the chelicerae spread apart and the fangs extended. The
lunges are sterotyped; they appear to be ritualized attacks which stop short of
their target or are sometimes directed slightly to one side of the target. Only one
lunging about (E3 X Ell) escalated into what approximated a real fight, but
neither spider was injured and the courtship eventually culminated in a successful
copulation.

Chase : very rapid pursuit of the other spider.

Retreat: movement which increases the distance between the spiders. It may
involve backing away or turning away (which may then continue as forward
movement).

Pause : interval between two actions when the spider is not moving. Pause
postures are variable.

Quivering, twitching, and body jerking : vibration-generating appendage (and
often body) movements which comprise a continuum. They are sometimes
difficult to distinguish from one another and may occur together in the same
bout. Twitching is one or a few distinctly separate sudden flexions or extensions
of one or more legs and/or pedipalps. Quivering is high frequency, usually low
amplitude, continuous twitching. Sometimes quivering involves only one or a few
appendages, but usually all legs and appendages are moving simultaneously.
Sometimes the entire body, especially the abdomen, quivers. Body jerking is a
particularly high amplitude twitching of all legs and pedipalps so that the entire
body jerks one or more times in succession. Female body jerking may visibly
vibrate the web and the male, even if he is several body lengths from the female.

Bouts which combine quivering, twitching, and even body jerking are common.
A courting male often begins low amplitude twitching which gradually increases
in frequency and amplitude to become a high amplitude quivering (or rapid
twitching). Sometimes a female’s legs quiver as she slowly flexes them and then
twitch as they are suddenly relaxed and reextended. At other times all her legs
and pedipalps twitch simultaneously and then quiver for a while. Sometimes a
female whose pedipalps and anterior legs are twitching or quivering will suddenly

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THE JOURNAL OF ARACHNOLOGY

shift to body jerking. Often the pedipalps and first legs appear to quiver or twitch
with greater amplitude than other appendages. Although quivering, twitching,
and body jerking are usually performed when the spider is not advancing,
sometimes a female will jerk-walk, jerking and quivering her appendages and
body while she walks through the web. Although most quivering, twitching, or
body jerking lasts for less than 1 or 2 s, occasionally a bout lasts longer; one
especially long bout (48 s) of virtually continuous quivering and body jerking was
performed by a female (H10) just before the final leg-fencing bout leading to
clasping.

Tapping-, repeated, rather rapid, non-synchronous lifting and lowering of the
pedipalps and first legs so that they contact the web forcefully. Tapping often
occurs just prior to or during advances and silk-walking. Sometimes tapping is
combined with quivering, or alternates with quivering or twitching bouts, or
occurs alone in the same behavioral context.

Silk-\valking\ jerky stop-and-go walk performed by the female during which she
periodically applies silk to the web. Silk-walking is often performed directly in
front of the male, and may continue all the way back to, and inside, her retreat.
Males were observed to briefly spin silk while courting only two times during this
study.

Leg-fencing-, semi-stereotyped sparring of the male with the female. The spiders
face one another and lower and raise and flex and extend their first and second
legs and pedipalps so that each spider’s appendages overlap, move past, and
brush against those of the other spider (Fig. 1). During leg-fencing the body is
often raised and lowered and the fangs are sometimes extended. The female
usually flexes her fencing appendages further, moves them more rapidly, and is
more likely to extend her fangs than is the male. The male’s legs tend to be more
extended and stiffer than those of the female; in general his movements appear
less aggressive and more protective than hers. Lunges sometimes occur during leg-
fencing. As a fencing bout proceeds, the male’s first legs may extend more fully
and decrease their movement as they prepare to slide into the clasping position.
During fencing the male usually raises and forcibly lowers his pedipalps (more or
less alternately) so that the cymbial apophyses punch down into the web. The
duration of leg-fencing bouts is quite variable (Table 2), but they usually last less
than 6 s.

Clasping: The clasping process begins during leg-fencing as the male gradually
raises, extends, and stiffens his first legs. He then advances a little to place each
of them between the nearest chelicera and pedipalp of the female. The mating
apophysis at the end of the male’s first tibia (Fig. 1) engages the base of the
female pedipalp prolaterally, presumably at either the trochanter or the coxal
endite (we were not able to observe the exact point of engagement). After the
claspers are engaged, the male continues advancing and tilts the female’s
cephalothorax up and back. During the clasping process, the male continues the
pedipalp tapping drumming that commenced during leg-fencing.

Palpal insertion attempts : Shortly after the clasping male has advanced so that
his chelicerae are nearly touching the female’s fourth leg coxae, he begins a series
of palpal insertion attempts. One pedipalp is lifted into position, fully extended,
and rotated (primarily at the coxa-trochanter joint) 100-120° (clockwise for the
left and counterclockwise for the right pedipalp) to position the palpal organ
above and ectal to the cymbium and close to the female’s genital opening (Fig. 2).

COYLE & O’SHIELDS— MATING BEHAVIOR OF THELECHORIS KARSCHI

287

Figures 1-2. — Courtship and mating behavior of Thelechoris k arse hi, side view, drawn from video
tape and preserved specimens; male dark, female light. Only appendages on near side are illustrated,
except for male’s left pedipalp. 1, leg-fencing. 2, copulation.

The other pedipalp is held semi-extended below the male. Periodic flexions of the
distal three joints of the active pedipalp lift the tibia and tarsus. These and
synchronous lateral movements at the patella-tibia joint and 90° twisting
movements of the palpal organ at its junction with the cymbium generate probing
thrusts (typically about one per s) of the long embolus close to the female’s
genital opening. A palpal insertion attempt bout consists of a series of these
thrusts which are sometimes interrupted by pauses. At the end of a bout the
active pedipalp is lowered to the resting position below the male and the other
pedipalp is lifted and a new bout of insertion attempts begins.

The following posture characteristics were consistently observed during these
palpal insertion attempts (Fig. 2): 1) The male’s chelicerae were touching or
almost touching the female’s fourth coxae. 2) The angle between the male and
female cephalothoraxes was 80-100°. 3) The female’s pedicel was flexed upwards
so that the cephalothorax-abdomen angle was 40-80°. 4) The male’s first legs
were bent approximately 90° at the femur-patella joint and the distal (clasping)
end of each tibia was against the prolateral surface of each female pedipalp base.
5) The female appeared to be cataleptic (motionless with legs and pedipalps partly
flexed) except for occasional quivering or other movements. During some
copulation attempts it was possible to see that the female’s genital area was
distended and the anterior and posterior genital lips were protruding and parted
so that the genital opening was more exposed than usual. The male’s second legs

Table 2. — Data for the 21 Thelechoris karschi courtships and copulation attempts that were video recorded. In the “palp insert” column, N means no
palpal insertions, Y means at least one insertion bout, and a question mark indicates that we could not be certain whether an insertion occurred. In the
“duration” column, “A” is the time from the first courtship behavior to the onset of leg-fencing, “B” is the time from onset of first leg-fencing to clasping,
and “C” is the duration of the copulation attempt (from clasping to uncoupling). Range, mean, and standard deviation given for leg-fencing durations.

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COYLE & O’SHIELDS— MATING BEHAVIOR OF THELECHORIS KARSCHI

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were either extending upward and outward against the web or upward and
forward to lightly contact the female’s first or second legs. Male legs III and IV
were usually extended (pushing) backwards and outwards against the web. If the
spiders were suspended in the web (probably the normal situation), the male’s
cephalothorax was horizontal or inclined slightly downward and his abdomen
was on nearly the same plane. However, if the pair was on solid substrate, the
male was typically under the front of the female with his cephalothorax inclined
upward at an angle of 35-75° and his abdomen nearly horizontal During one
apparently unsuccessful copulation, the pair maintained this posture (relative to
one another) while gradually rotating 1 10° onto their sides.

A successful insertion bout begins with the insertion attempt movements
described above. Then, as the embolus tip enters the genital opening, these earlier
movements stop and the three distal palpal joints flex to insert the entire length
of the embolus into the opening (Fig. 2). Occasionally the palpus is held
motionless in this inserted position for awhile, but more commonly the pedipalp
performs repeated pulsing flexions (of the distal joints), each of which visibly
pulls and twists the female’s abdomen toward the male. During this series of
alternate flexions and extensions, the embolus is never withdrawn from the
genital opening, indeed its sliding movement within the female genitalia appears
minimal. One such series of 20 flexions by an inserted palp lasted 38 s. Another
much longer series (274 s) of slower and less regular palpal flexions involved one
flexion every 2-5 s.

Uncoupling: pulling away of one spider from the other to end the copulation
attempt.

Figure 3 summarizes our observations on the sequence of both male and female
behaviors during courtship and mating in T. karschi. The courtship and mating
process can be divided into two phases. Phase I includes non-contact behaviors
and phase II includes behaviors which involve contact (or virtual contact)
between male and female. Transition from phase I to phase II necessitates an
advance into contact. Retreats and chases are transitional behaviors that shift the
courtship from phase II back to phase I.

Male activity in phase I is primarily cyclic, i.e., a series of short advances, or
quivers then advances, or quivers, with each action separated by a pause of highly
variable duration. This cycle of male activity ends when contact with the female
leads to leg-fencing and/or lunges (phase II behaviors). Re-entry to this cycle may
occur after retreats from contact courtship (phase II). Often, female behaviors
(quivers, silk-walking, advances) follow the retreats and appear to trigger a new
cycle of male non-contact signaling.

Ninety percent of the time that the spiders advance into contact from phase I
behavior, leg-fencing or lunges occur. Sooner or later these phase II behaviors
usually lead to retreats back to phase I courtship; only 23% of the leg-fencing
bouts we observed led directly to clasping. The number of leg-fencing bouts
performed before a courtship proceeded to clasping varied from 1 to 17 (Table 2).

From courtship to courtship, there is much variation in the amount of lunging.
Both male and female lunging were common in only 6 of the 17 courtships for
which we have complete video records of contact courtship (Table 2). None of the
spiders (E3, E6, Ell) that mated with more than one mate were consistently
aggressive or non-aggressive in all courtships. In two (E6 X Ell) of the three
encounters with a sequential series of multiple courtships and matings for which

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MALE PLACED IN WEB
(NO MOVEMENT)

Figure 3. — Summary of the sequence of Thelechoris karschi courtship and mating behaviors, based
on an analysis of the 21 courtships and copulation attempts recorded on video tape. Male behaviors
in boxes; female behaviors in ellipses. Arrows indicate sequence and numbers indicate the percentage
of times a particular behavioral unit is followed by another. Quiver boxes and ellipses represent not
only quivering, but also related behavioral units commonly associated with quivering, i.e., twitching,
body jerking, and some forms of tapping. Although both male and female frequently pause during
courtship and mating, only the male pauses which occur repeatedly during the non-contact phase of
courtship are included in this diagram.

COYLE & O’SHIELDS— MATING BEHAVIOR OF THELECHORIS KARSCHl

291

we have complete video records, there was a drastic decrease in lunges after the
first courtship of each series; the other such encounter (E5 X Ell) involved no
lunging. The courtship lunging of female Ell, which mated successfully on four
different days during a four-week period, decreased gradually and drastically
during that period.

Overall, we observed 105 female and 67 male lunges. In four of the six
courtships with many lunges, females lunged considerably more often than males.
The amount of lunging tends to be correlated with the amount of leg-fencing,
which is a consequence of the fact that lunges tend to precede, follow, and/or be
nested within leg-fencing bouts. A higher proportion of female lunges (71%) than
male lunges (37%) were nested in leg-fencing; females lunged 3.2 times more often
than males during leg-fencing. The male lunge box and female lunge ellipse in
Fig. 3 represent individual lunges or bouts of repeated lunges that were not
nested within a leg-fencing bout. Although lunges are sometimes followed by full
retreats from contact courtship, most lunges are followed by other lunges or leg-
fencing; these lunges usually cause the other spider to momentarily reel backward,
but we did not count this as a retreat since the spider rebounds instantly.
Sometimes lunging was reciprocal; sometimes it was not, with two or more
female lunges (common) or two or more male lunges (less common) in succession.
Chasing, which occurred only in courtships with much lunging, was performed
only by females.

The transition from leg-fencing to clasping to palpal insertion attempts occurs
rather quickly. The clasper positioning process lasts from 2 to 15 s (mean = 5.4,
SD = 2.9 TV = 17) and the period between the completion of clasper attachment
and the first palpal insertion attempt lasts from I to 30 s (mean = 6.8, SD == 6.7,
TV = 16). Following the onset of clasping, female leg-fencing rapidly decelerates
and shifts to quivering so that by the first palpal insertion attempts, she exhibits
the typical cataleptic copulatory posture (Fig. 2). The only time this did not occur
was when a male (E6) was clasping the female (El 7) abnormally (with only his
left first leg); she extended her fangs and pushed him away while he was reaching
with his pedipalps to initiate insertion attempts.

The recorded courtships and copulation attempts varied widely in duration
(Table 2). Successful copulations were significantly longer ( TV = 8, range = 6.67-
108.85 min, mean = 40.39, SD = 38.4) than the clearly unsuccessful copulation
attempts (TV = 4, range = 0.47-5.03 min, mean = 2.90, SD = 2.5) and the
copulation attempts of questionable success (TV = 9, range = 1.30-26.00 min,
mean = 6.79, SD = 7.8) (F< 0.01, Mann-Whitney U).

Unsuccessful copulation attempts consisted of a series of unsuccessful palpal
insertion attempt bouts and occasional pauses within bouts or between bouts
when neither pedipalp was moving (usually both pedipalps were lowered). Even
within one copulation attempt, these insertion attempt bouts varied considerably
in duration. For example, in one apparently unsuccessful copulation attempt (E3
X H10) there were 22 bouts of unsuccessful insertion attempts and these bouts
ranged from 2 to 34 s (mean = 10.5, SD = 7.4) in duration.

Successful copulations involved bouts of unsuccessful palpal insertion attempts
and one or more bouts with successful insertions. These successful insertion bouts
did not occur at the beginning of a copulation, and were more common during
the second half than during the first half of a copulation attempt. Successful
insertion bouts typically lasted longer (range = 58-277 s, mean = 111.8, SD =

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68.0, N = 13) than unsuccessful bouts (range = 2-87 s, mean = 18.0, SD = 19.5,
N = 35) ( P < 0.01, Mann-Wfaitney U ). Marked left-right asymmetry in palpal
insertion attempts was observed in two successful copulation attempts (E6 X Ell,
E3 X Ell); in both cases the left palp became tangled in silk and only the right
palp (with longer insertion attempt bouts than the left) achieved successful
insertions. Since it was not possible to observe every insertion attempt bout
carefully enough to determine whether it was successful, we could not determine
the ratio of successful to unsuccessful insertion bouts for the seven successful
video-recorded copulation attempts (Table 2).

During a few of the copulation attempts, the male occasionally shifted his legs
and body and moved the female, usually pushing her further upwards and
backwards. During nearly all the copulation attempts, the female was motionless
except for occasional quivering of her legs and pedipalps. On only three or four
occasions during the 21 copulation attempts we observed did the female
perceptibly shift her legs and body position. Female quivering was most likely to
occur at the very beginning of a copulation period, during pauses within or
between palpal insertion attempt bouts, and was more common during
unsuccessful copulations than during successful ones. The longest and most
intense female quivering (three long periods of especially high amplitude whole-
body quivering) occurred during one short (4.47 min) unsuccessful copulation
attempt (E5 X El 1).

Approximately equal numbers of male uncouplings and female uncouplings
followed both successful and unsuccessful copulations (Table 2). None of the
uncouplings was followed immediately by a female attack. Following three of the
male-initiated uncouplings, the female remained cataleptic for at least 2 s.

A survey of the structure of the palpal organ and spermathecae of T karshci
demonstrates that the embolus, when fully inserted into the genital opening
during the successful insertion attempts described above (Fig. 2), should extend
far into one of the four spermathecal stalks and possibly into the bulb (Figs. 4,
5). The curved, slender, and semi-flexible nature of the embolus may permit it to
conform to the lumen of the spiraled spermathecal stalk as it is inserted and/or
the stalk may be flexible enough to uncoil at least partly during this insertion. Of
the eight females with sperm, five had all four spermathecal stalks and bulbs
filled; the other three each had one stalk/ bulb unit empty of sperm and the other
three filled.

DISCUSSION

Our field data hint that male maturation in I karschi may be regulated so that
mating occurs just before or during the rainy season, but the Humboldt Museum
(Berlin) collection contains a large number of males collected in 1907 by Scheffler
just 40 miles north of population E between July and October in the dry season.
The apparent high ratio of adult females to adult males observed in population E
during the breeding season is probably characteristic of mygalomorph spiders in
general and may, because of the increased mating opportunities for males, have
important effects on their courtship and mating strategies (Coyle 1986b).

Although we did not design this study to test rigorously for behavioral
isolation among the populations observed, two results provide support for the
hypothesis that these populations are conspecific: 1) the absence of obvious

COYLE & O’SHIELDS— MATING BEHAVIOR OF THELECHORIS KARSCHI

293

Figures 4-5. — Male and female genital organs of Thelechoris karschi drawn to same scale. 4, left
male palpal organ, ventral and slightly retrolateral view with the embolus in horizontal plane. 5,
female genitalia showing outline of anterior genital lip, bursa copulatrix, and the four spermathecae
with coiled stalks and bulbs in horizontal plane.

differences in courtship signals among the males (populations A, C, D, and E)
and females (populations B, D, E, F, G, and H), and 2) the presence of palpal
insertions between individuals from populations A and E, B and E, C and E, D
and E, and E and G. The low frequency (31%) of encounters resulting in
copulation attempts is perhaps not surprising in view of the unknown and surely
varied reproductive histories of the subjects, the 2- to 23-week hiatus between
collection and observation, and the lack of strictly natural conditions.

The possible functions and origins of the courtship behavior patterns of T.
karschi deserve comment. The male quivers and advances are probably distinct
enough from prey struggles to generate vibrations that inhibit the predatory
response of receptive females, and the female quiver response appears to
encourage the male to continue courting. Such vibratory courtship signals are
common among spiders and may, as Robinson and Robinson (1980) suggest, be
ritualized conflict behaviors shaped from locomotor hesitancy in situations where
both attack and flee control centers are active. Lunging appears to be ritualized
agonistic behavior and, as we suggest later, may play a role in assessment of male
fitness. The same may be true of leg fencing, but its function and origin might be
more closely linked to clasping behavior. The female silk-walk, which appears to
foster renewed male courting after a retreat from contact courtship, might be
ritualized web maintenance behavior. Clasping, a male mating behavior
widespread among mygalomorph taxa, may serve to protect the male, to position
and steady the mating pair for more effective sperm transfer, and/or to convince
the female to permit palpal insertions (Eberhard 1985; Coyle 1986). The rejection
of male E6’s palpal insertion attempt by female El 7, when only one of his two
claspers was positioned properly, supports the third function. Clasping may be a
ritualized form of the defensive rearing response common to virtually all
mygalomorphs. Male palpal tapping during leg fencing and clasper positioning
may help convince the female to permit clasping.

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A number of the courtship and mating behavior units of T. karschi are similar
in form, context, and presumably function (and are perhaps homologous) to
behaviors observed in one or more of the four other diplurid taxa whose
courtship and mating behaviors have been described ( Microhexura monitvaga
(Coyle 1985), Euagrus (Coyle 1986b), Australothele jamiesoni (Raven 1988), and
Phyxioschema suthepia (Raven and Schwendinger 1989)). Males of at least the
first three of these taxa rely upon similar vibratory signals, especially jerking and
quivering. The “jerking bouts” of M. montivaga , the “jerk-quivers” of Euagrus ,
and the body jerking and anterior leg-trembling behavior of A. jamiesoni involve
more vigorous up and down motion of the whole body and are more stereotyped
than the quivering and twitching patterns of T. karschi. Perhaps the tapping/
drumming of pedipalps by T. karschi males is homologous to the pedipalpal
drumming performed by A. jamiesoni. Leg fencing appears similar to the “leg-
grappling” of M. montivaga , and resembles the onset of clasping in Euagrus and
A. jamiesoni. The drumming and quivering of pedipalps and first legs by Euagrus
females occurs in the same context (serves the same function?) as the tapping,
quivering, twitching, and jerking behavior of T. karschi females. Behavior
resembling the silk-walking of T. karschi females has been observed during
unsuccessful M. montivaga courtships but not at all in Euagrus or A. jamiesoni.
The mating posture of T. karschi is the front-to-front posture typical of non-
araneomorph spiders; in its details it is much more similar to that of M.
montivaga than to the postures observed in Euagrus , A. jamiesoni , and P.
suthepia , all of which employ mating claspers found on the male’s second leg.
The female catalepsis and alternate palpal insertion attempts characteristic of T.
karschi copulation attempts were observed in M. montivaga and Euagrus
(catalepsis) and in M. montivaga and A. jamiesoni (alternate insertions).

It is important to realize that the risk to T. karschi males of female-inflicted
attacks and injury is probably lower in nature than in the confines of a mating
arena. Although the data suggest that males are at risk during all stages of
courtship and mating, from the time they enter the female’s web until they depart,
they also indicate that T. karschi males are not in as much danger of attack
immediately after uncoupling as are the males of Euagrus and P. suthepia (Coyle
1986b; Raven and Schwendinger 1989).

The occurrence of both aggression-rich and aggression-poor successful
courtships in T. karschi is of particular interest. Although the aggressive
behaviors (lunging and leg-fencing) appear to be ritualized and therefore not very
risky, they may increase the cost (in time and energy) of aggression-rich
courtships when compared to the aggression-poor courtships. The proclivity of T.
karschi males to lunge at females and to continue or resume courting in spite of
female lunges and chases is a phenomenon not yet observed in other diplurids
(Coyle 1985, 1986b, in prep.; Raven 1988). Perhaps these hawk-like interactions
are fostered by females (who tend to lunge more often than the males) and serve
to test the males’ fitness. The sudden drastic decrease of aggression twice
observed in the second consecutive courtship of a pair (E6 X Ell) might indicate
that once a male has “convinced” a female that he is fit, she no longer tests him.
Possibly leg fencing bouts constitute a more highly ritualized test of aggressive
fitness than lunges, and supply the female with adequate fitness information in
those courtship encounters devoid of lunges. Alternatively, it may be true that the
observed variation in aggression is the result of variation in female receptivity

COYLE & O’SHIELDS— MATING BEHAVIOR OF THELECHORIS KARSCHI

295

caused by habituation or other factors not necessarily related to sexual selection
by female choice.

The observed willingness of female T karschi to accept copulation attempts
from more than one male is a prerequisite for sexual selection of male anatomical
and behavioral traits associated with clasping and copulation (Eberhard 1985).
Our observations that a female may reject a male which has not “properly”
clasped her (E6 X El 7) and that palpal insertion attempts often do not lead to
successful insertion are consistent with Eberhard’s hypothesis that sexual selection
by female choice commonly occurs during copulation attempts. It is possible that
the female, even though largely cataleptic, may be providing mechanical
challenges to the male’s copulatory ability, monitoring his performance, and
adjusting her behavior and/or physiology to maximize her fitness. If this is not
happening, it seems even harder to understand why such a large fraction of palpal
insertion attempts are unsuccessful and why females sometime quiver during
pauses in male activity within copulation attempts.

The ability of T. karschi males to attempt copulations repeatedly over a period
of days with different females is consistent with the apparent high ratio of adult
females to adult males, with observations of other diplurids (Coyle 1985, 1986b,
in prep.), and with the general pattern of male promiscuity in animals. It is not so
easy, however, to understand why males which have achieved successful insertions
in one copulation bout will continue to court and attempt additional copulations
with the same female unless sperm is not always transferred during a successful
insertion or unless, as our observations suggest, a single successful insertion (and
sperm transfer) bout is not sufficient to fill all four of his mate’s spermathecae. If
either or both of these constraints exist, a large number of copulation attempts
might be required to fill her spermathecae sufficiently to 1) fertilize all of her eggs
and/or 2) inhibit her motivation to mate with other males (and, therefore, to
guarantee his paternity).

We suspect that the mechanics of sperm transfer in T. karschi make it difficult
for a male to fill all four of a female’s spermathecae in one copulation attempt.
Given the long embolus, the dimensions of the bursa copulatrix and spermathecae
(Figs. 4, 5), the observation that the entire embolus is inserted, and the
observation that the embolus is not withdrawn during an insertion bout, each
successful palpal insertion bout can probably deliver sperm to only one of the
four bulbs. Add to this the additional possibilities that 1) the male may have
difficulty directing the embolus tip into a particular unfilled stalk at will and 2)
the right pedipalp is probably designed to insert into the pair of spermathecae on
one side and the left pedipalp into the other pair, and it becomes even more
apparent why it might normally take more than one copulation attempt for a
male to fill all four spermathecae.

In general, our observations of T karschi behavior suggest that the functions of
courtship may continue to be performed after the onset of clasping and during
the copulation attempt that follows. The large amount of copulatory effort
required per successful insertion may be partly the result of this spider’s genital
morphology or of female testing of male copulatory performance or both. Clearly
much more information is needed about the physiology and functional
morphology of reproduction and about the behavioral ecology of natural
populations of this species before our observations can be understood and the
questions they have generated can be answered.

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ACKNOWLEDGMENTS

We are grateful to Robb Bennett for helping to collect the spiders used in this
study, to Richard Bagine and The National Museums of Kenya for logistical
assistance, to Cornell Dudley and his wife for their hospitality in Malawi, to
Nancy Reagan and Ted Meigs for their comments on an early draft of this paper,
and William Eberhard and Michael Robinson for helpful criticism of the
manuscript. This study was supported by National Science Foundation Grant
BSR-8700298.

LITERATURE CITED

Coyle, F. A. 1985. Observations on the mating behavior of the tiny mygalomorph spider, Microhexura
montivaga Crosby and Bishop (Araneae, Dipluridae). Bull. Br. Arachnol. Soc., 6(8):328-330.

Coyle, F. A. 1986a. Chilehexops, a new funnelweb mygalomorph spider genus from Chile (Araneae,
Dipluridae). Amer. Mus. Novitates, (2860): 1-10.

Coyle, F. A. 1986b. Courtship, mating, and the function of male-specific structures in the
mygalomorph spider genus Euagrus (Araneae, Dipluridae). Proc. Ninth Internal. Congr.
Arachnology, pp. 33-38.

Eberhard, W. G. 1985. Sexual Selection and Animal Genitalia. Harvard Univ. Press, Cambridge. 244 pp.

Raven, R. J. 1985. The spider infraorder Mygalomorphae (Araneae): cladistics and systematics. Bull.
Amer. Mus. Nat. Hist., 1 82( 1 ): 1 - 1 80.

Raven, R. J. 1988. Preliminary observations on the mating behaviour of the Australian mygalomorph
spider Australothele jamiesoni (Dipluridae, Araneae, Arachnida). Mem. Queensland Mus.,
25(2):47 1-474.

Raven, R. J. and P. J. Schwendinger. 1989. On a new Phyxioschema (Araneae, Mygalomorphae,
Dipluridae) from Thailand and its biology. Bull Brit. Arachnol. Soc., 8(2):55-60.

Robinson, M. H. and B. Robinson. 1980. Comparative studies of the courthsip and mating behavior
of tropical araneid spiders. Pacific Insects Monogr., 36:1-218.

Manuscript received January 1990, revised April 1990.

Lombardi, S. J. and D. L. Kaplan. 1990. The amino acid composition of major ampullate gland silk
(dragline) of Nephila clavipes (Araneae, Tetragnathidae). J. Arachnol., 18:297-306.

THE AMINO ACID COMPOSITION OF MAJOR AMPULLATE
GLAND SILK (DRAGLINE) OF NEPHILA CLAVIPES
(ARANEAE, TETRAGNATHIDAE)

Stephen J. Lombardi and David L. Kaplan

U.S. Army Natick Research, Development,
and Engineering Center, Biotechnology Branch,
Science and Advanced Technology Directorate
STRNC-YMT, Natick, Massachusetts 01760-5020 USA

ABSTRACT

Amino acid composition of major ampullate gland silk (dragline) produced by the mature, female
golden orb-weaving spider, Nephila clavipes was determined. Several solvents were applied in order to
solubilize the spider silk. Although several strong acids and bases were able to solubilize silk, the
protein was apparently degraded by this treatment, as demonstrated by protein gel electrophoresis.
Only a mixture of hydrochloric/propionic acid (50:50, v:v, final concentration 3N HCL/25%
propionic acid) solubilized the silk while retaining the molecular weight integrity of the crystalline
polymer. The results show that the major ampullate gland secretion is characterized by a high degree
of small side chain amino acids (Ala, Gly, and Ser) and polar residues (Gly and Arg), comprising
almost 75% of the total amino acids present. Contrary to published findings (Work and Young 1987),
the composition of major ampullate gland silk appears to be uniform within the species. The
composition of the secretion is discussed in relation to the known and implied functions of the major
ampullate gland as well as in relation to the mechanical properties of the silk produced by orb-web
building spiders.

INTRODUCTION

Spiders are unique in their ability to synthesize and utilize silks for a variety of
purposes. The orb-web spinners are equipped with 5-7 different types of silk
secreting glands, each synthesizing its own type of silk to be utilized for a specific
purpose, e.g., construction of the dry and sticky parts of the web, construction of
the egg-sac, and swathing silk of captured prey (Gosline et al. 1984). These fibers
are synthesized by extremely specialized glands situated in the abdominal cavity.
Although the amino acid composition is known for the seven silks from one
animal (Andersen 1970), only two of the seven types of silk have been
investigated in any detail. Nephila clavipes is a large, orb-weaving spider,
dispersed in the tropical and subtropical areas of the western hemisphere (Moore
1977). Their most prominent glands are a pair of large major ampullate glands
which secrete the protein for dragline silk. Three morphological regions
distinguish the gland: the tail, ampulla, and duct. The tail is the site of
approximately 90% of the major ampullate gland’s protein synthetic activity; the
ampulla is a storage site for soluble dragline silk; and the duct appears to be
involved with secretion and ordering of silk (Bell and Peakall 1969). It can be
assumed that the mechanoelastic properities of the silk fibers correlate closely

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with their functional properties and that these properties are in turn determined
by their chemical composition and molecular conformation. The multiformity of
material makes spider silk ideal for studies on the relationship between chemical
composition, structural conformation, and mechanoelastic properties of biological
fibers.

The term fibroin is often used for the silk fibers secreted by some insects and
arachnids (Lucas et al. 1958). Studies on the chemistry of insect and arachnid
fibroins have been previously reported by Rudall (1962), Lucas et al, (1960),
Andersen (1970), Hunt (1970), Hazan et al, (1975), Tillinghast and Christenson
(1984), and Work and Emerson (1987). Data on Nephila silk amino acid
composition is limited. Amino acid composition has been reported to a lesser
degree for Nephila senegalensis (Walkenaer) (Lucas et al. 1960), Nephila
madagascariensis (Vinson) (Lucas et al. 1960), and N. clavipes (Zernlin 1967;
Tillinghast and Christenson 1984). The silks of these organisms appear to be
composed of anti-parallel beta-pleated sheets but have different intersheet
distances (Warwicker 1960). These investigations imply that the silks vary in
composition and properties, but there is insufficient information to make a
definitive correlation between chemical composition and structural properties. X-
ray diffraction patterns (Gosline et al. 1984, 1986) have implied that the
molecular conformation of major ampullate gland fibers consists of crystalline
regions dispersed in a matrix of amorphous proteinaceous material. The ratios of
crystalline to amorphous regions may be a crucial factor in the assessment of
physical properties of the fiber.

The objectives were to (1) develop a system by which silk fibers obtained by
controlled silking could be completely solubilized while retaining the molecular
weight integrity of the fiber, (2) determine the amino acid composition in major
ampullate gland silk (MaAS) of N. clavipes , and (3) search for correlations
between MaAS chemical composition and physical properties of these fibers. In
this paper we describe the results of amino acid composition analysis of the
dragline silk if N. clavipes and bring out the importance of the relationships
between chemical composition and physical properties.

MATERIALS AND METHODS

Species. — Samples were collected from the following araneid species, N.
clavipes Nephilinae were kindly supplied by Angela Choate, University of
Florida, Gainesville, FLA; Argiope aurantia (Lucas) and Neoscona domiciliorum
(Hentz) were supplied by Mark Stowe, University of Florida, Gainesville, FLA.
Specimens were kept alive in individual cages and fed a diet of German
cockroaches, Blatella germanica (Blattellidae).

Silk collection. — Controlled silking was performed as described by Work and
Emerson (1982). Controlled silking was restricted to the spiders which were large
enough to be easily manipulated without damaging the spider. The silking
procedure averaged 30 minutes and 5.0 milligrams (mg) of MaAS was routinely
obtained. The mature females were continuously observed under 60X
magnification to substantiate the glandular source of silk. All reeled samples were
examined using a Zeiss light microscope (1250X total magnification) to ensure
that there was no contamination by minor ampullate gland fibers.

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299

Silk solubilization. — Silk samples ( 1.0-2. 0 mg) were placed in 13 X 100 mm
sterile glass borosilicate test tubes. The solvents listed in Table 1 were added to a
final concentration of 1.0 ug/ul and solubility determined visually at room
temperature.

Removal of solvent. — After solubilization the samples (reeled or glandular)
were either dialyzed against 100 ml of 10 mM Tris-HCl, pH 7.0 for 24 h or dried
immediately under vacuum (purged with argon) and reconstituted in the Tris
buffer (final concentration 1 ug/ul).

Silk hydrolysis. — Major ampullate gland silk (reeled samples, 2.0 mg) were first
dissolved in 2.0 ml of a hydrochloric/ propionic acid mixture at room temperature
for 20 min with slight vortexing. Solubilized samples (100 ul at 1.0 ug/ul) were
vacuum dried in pyrolyzed vials and purged with argon gas. Hydrolysis was
carried out by placing 200 ul of constant boiling 6N HC1 in the bottom of the
reacti-vial along with two sodium sulfite crystals. The vessel was again purged
with argon gas, sealed under vacuum and placed at 150 °C for 1 hour. Argon was
used as a purging gas because of its purity and because it contributes fewer
artifact peaks in the subsequent analysis. Sodium sulfite is used as an oxygen
scavenger and aids in the recovery of cysteine, serine, and threonine. The oxygen
scavenging activity of the crystals in the reaction aids in avoiding non-specific
hydrolysis of amino acid residues and subsequent amino acid degradation at the
elevated temperatures (Ted Tanhauser personal communication).

Amino acid analysis. — Multiple analyses were carried out on a Waters HPLC
Pico-Tag Amino Acid analysis system. The hydrolyzed samples were derivatized
with phenylisothiocyanate (PITC) and these samples reconstituted in 400 ul of
sample diluent. For each analysis a 50 ul injection volume was used. Amino acid
standards were run with each sample. Ribonuclease A was run as an hydrolysis
control.

Glandular dissection. — Major ampullate glands (tail, ampulla, and duct) were
dissected out of living spiders through a 1.5 cm longitudinal incision along the
ventral abdomen. The glands were removed carefully to avoid degradation of the
luminar contents. The glands were immediately transferred to a medium
containing 0.10M sodium chloride and 0.015 M sodium citrate (SSC). Protease
inhibitors, phenylmethyl sulfonyl flouride (PMSF) at a final concentration of 6-10
mg/ ml (Weber et al. 1972) and 20 units/ ml of aprotonin (Piperno et al. 1979),
were added to the dissection buffer to inhibit proteases released by the gastric
system of the spider. Solubilization, hydrolysis, and amino acid analysis were
performed as previously described.

RESULTS

Silk solubility. — Of the solubilizing agents studied, only hydrochloric/ propionic
acid (50:50, v:v) dissolved N. clavipes dragline silk at room temperature with only
slight agitation (Table 1). Hydrochloric acid below 6N and used alone failed to
completely dissolve the silk even at elevated temperatures (data not shown). Some
quarternary ammonium compounds used as commercial tissue solubilizers proved
to be efficient solvents, but the solvent could not be easily removed from the
solution. High concentrations of base also dissolved silk samples, although they
were not used because the elevated temperatures needed for solubilization may

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Table 1. — Solubility of Nephila clavipes dragline silk in various solvent systems. 1 ■ Totally
insoluble, 2 = Partially soluble, some particulates, 3 Partially soluble, no particulates, viscous
suspension, 4 = Totally soluble, no particulates, clear, non-viscous.

Solvent

Solubility at
room temperature

Water

-1

1NHC1

2N HC1

-1

3N HC1

-1

4N HC1

-2

5N HC1

-2

6N NC,1

-1+2

IN KOH

-1

Chloroform

”1

Ethyl alcohol 95%

-1

8M Urea

-2

50% Lithium Bromide

—2

1% SDS

-1

5% Mercaptoethanol

-1

Soluene

Constant boiling 6N H Cl / 50% Propionic acid

begin random hydrolysis of the silk backbone prior to amino acid hydrolysis.
Any amino acids hydrolyzed prior to the 150 °C hydrolysis reaction may then
become completely degraded at the hydrolysis step and subsequently unaccounted
for in the final analysis (Ted Tanhauser personal communication).

Hydrochloric/propionic acid proved to be most suitable; it solubilized the silk
immediately and more importantly retained the molecular weight integrity of the
silk as determined by polyacrylamide gel electrophoresis and high performance
liquid chromatography (data not shown).

Amino add analysis. — The amino acid composition of the secretion of (MaAS)
from N. clavipes is shown in Tables 2 and 3. Glycine, alanine, glutamic acid/
glutamine, and arginine were the most abundant amino acids, together
comprising 74 percent of the total amino acids present. Generally, the major
ampul late gland silk has been considered for use in the production of dragline,
frame threads, and radii of the web. The dragline has a high tensile strength (198
grams per denier, gpd) and it has a rupture elongation of 18% (Zemlin 1967). The
composition of the material from the large ampullate gland (pulled and
glandular) generally agrees with the published analyses of dragline from N.
clavipes (Zemlin 1967; Work and Young 1987), but some differences are observed.
Work and Young 1987, report extremely low levels of asparagine, threonine,
arginine and valine (0.87, 0.31, 1.37, and 0.76 respectively). We report
significantly higher levels of these residues (see Table 2), theorizing that these
residues play important roles in the amorphous domains of the polymer.
Deoxyribonucleic acid (DNA) sequencing of the MaAS gene has confirmed the
presence of these residues.

Table 3 shows the amounts of various amino acid side chains in dragline silk of
N. clavipes . Dragline silk is composed predominantly of the small side-chain
amino acids glycine, alanine, and serine, which would allow them to conform to
the antiparallel beta-pleated sheet model proposed by Pauling and Corey (1953)
for Bombyx mod. The conformational model applies only to the crystalline

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301

Table 2. — Amino acid composition of reeled dragline silk of Nephila clavipes. Results expressed as
residues per 100 total. Three trials each spider.

Amino acid

Spider 1

Spider 2

Spider 3

Asp/ Asn

(D/N)

2.5

2.4

2.6

G lu/ Gin

(E/Q)

9.1

9.0

9.2

Ser

(S)

4.5

4.4

Gly

(G)

37.0

37.3

36.9

His

(H)

0.5

0.4

Arg

(R)

7.6

7.7

Thr

(T)

1.6

1.7

1.6

Ala

(A)

21.1

21.0

21.2

Pro

(P)

4.3

Tyr

(Y)

3.0

3.2

Val

(V)

1.8

1.7

Met

(M)

0.3

0.2

Cys

0.1

<0.1

Ile

(I)

1.0

Leu

(L)

3.8

3.7

Phe

(F)

0.7

Lys

(K)

1.0

regions of B. mori , which makes up approximately 40% of the total silk structure,
as described by x-ray diffraction analysis (lizuka 1965). Limited x-ray diffraction
data has been reported which describes the degree of crystallinity in dragline silk
of certain araneid species, (Gosline et al. 1984, 1986, 1988).

We thought it worthwhile to look at the pulled draglines from other spider
species, Argiope aurantia and Neoscona domiciliorum , and look for
comparisons/ differences in the amino acid compositions. Reeled samples of
dragline silk were prepared as previously described. Table 4 shows the differences
in the amino acid composition of the various draglines as compared to Nephila
clavipes reeled dragline. Generally, Argiope and Nephila dragline silks are quite
similar, although Nephila contains many more arginine residues (7.6% vs 2.9%).
The arginine residue appears to be an important component of the amorphous
domain repeating segment, as seen in DNA sequencing of the dragline silk gene
(unpublished data). Neoscona dragline also has a similar amino acid composition

Table 3. — Amounts of various amino acid side chains in reeled dragline silk of Nephila clavipes.
Results expressed as residues per 100 total. Small side chains: gly + ala + ser, polar residues: asp +
glx, basic side chains: lys + his + arg cyclic imino side chain: pro, aromatic side chain: phe + tyr,
sulfur containing: met + cys, aliphatic side chain: ala + val + ile, hydroxyl side chain: ser T thr.
Three trials each spider.

Dragline silk

Spider 1

Spider 2

Spider 3

Small side chains

62.28

62.92

62.59

Polar side chains

29.81

29.61

30.22

Acidic/ amide side chains

11.67

11.52

11.83

Basic side chains

9.05

9.02

9.06

Cyclic imino side chain

4.3

4.34

4.28

Aromatic side chain

3.62

3.57

3.88

Sulfur containing

0.47

0.46

0.22

Aliphatic side chain

27.61

27.57

26.62

Hydroxyl side chain

6.16

6.20

6.09

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Table 4. — Amino acid composition of the silk gland secretions of various spiders. Results expressed
as residues per 100 total residues.

Amino

acid

Nephila

clavipes

Argiope

aurantia

Neoscona

domiciliorum

Dragline

(reeled)

Glandular

(MaAs)

Dragline

(reeled)

Dragline

(reeled)

Asx

2.5

2.1

1.6

0.6

Glx

9.2

8.3

11.1

10.0

Ser

4.5

3.9

5.1

6.8

Gly

37.1

38.1

34.7

38.0

Arg

7.6

7.2

2.9

0.6

Thr

1.7

2.0

0.8

0.9

Ala

21.1

23.4

22.2

18.0

Pro

4.3

3.9

6.4

11.2

Tyr

2.9

4.3

3.8

3.7

Val

1.8

1.7

1.5

0.7

Met

0.4

0.3

0.2

Cys

0.1

0.9

0.3

0.7

0.9

0.5

0.8

0.5

Leu

3.8

4.0

4.2

1.2

Lys

0.5

1.0

0.5

0.2

profile to Nephila , but does contain almost three times as many proline residues
(4.3% vs 1 1.2%).

Table 4 also compares the amino acid composition between reeled and
glandular sources of Nephila clavipes dragline silk. The data clearly shows the
profiles are virtually identical in composition. Samples were prepared for analysis
as described in materials and methods.

DISCUSSION

One of the most difficult problems in the study of structural proteins (e.g., silk,
collagen, elastin, resilin, and keratin) is solubilization without degradation of the
polymer (Lucas et al. 1958). N. clavipes dragline silk, like other insect and
arachnid fibroins, does not dissolve in water; nor does It solubilize at room
temperature in most of the solvents described in Table 1, except for the strong
acids and Soluene. Soluene could not conveniently be removed from the silk
solution and was deemed unsuitable in any further analysis.

The solubilization effect of hydrochloric/ propionic acid treatment on spider
silk is almost instantaneous at room temperature. Hydrolysis of the protein
backbone does not appear to take place as a result of solubilization in strong
acids (6N HCL/ Propionic acid). The molecular weight integrity of the polymer
was maintained as observed by polyacrylamide gel electrophoresis; a single,
homogeneous band of approximately 350,000 daltons was observed, in both acid
solubilized reeled silk and from luminar contents isolated from dissected major
ampullate glands. Hydrochloric/ propionic acid may act as a strong oxidizing
agent. The amino acids most affected by oxidation are cysteine, methionine, and
tyrosine. Cysteine was initially presumed to be destroyed over time, but the use of
hydrolysis controls in the analysis indicated this was not the case. More
importantly, it appears that disulfide bridges do not play a role in maintaining

LOMBARDI & KAPLAN— AMINO ACIDS IN NEPHILA CLAVIPES SILK

303

the structural integrity of silk for two reasons: (1) the overall absence of cysteine
(<0.50%) in the amino acid analysis, and (2) the insolubility of the silk in
mercaptoethanol Methionine also appears to have little influence on the
secondary structure, since the total amount of this amino acid (< 0.50%) is too
small and methionine is not implicated in crosslinking in any characterized
protein.

The content of tyrosine, however, is more interesting. This amino acid residue
appears unaffected in dragline silk hydrolysis and analysis (3.0%). Two plausible
hypotheses may be presented, both indicating that tyrosine plays a specific role in
preserving the secondary structure of spider silk: (i) spider silk tyrosine is
protected against oxidation either by its position inside the hydrophobic moiety
of the molecule, or by an electrophilic substitution at the el or e2 positions of the
phenolic hydroxyl, (ii) any oxidized tyrosines are not completely degraded and
complexed in the derivatization reaction, thus remaining unseparated from
tyrosine in subsequent analysis. The latter seems unlikely due to the presence of
oxygen scavengers in the hydrolysis reaction, which aid in recovery of certain
amino acids. The former appears to be logical explanation. Parallel experiments
were performed omitting sodium sulfite and hydrolysis controls; subsequently the
recovery of tyrosine was unaffected by potential oxidation reactions.

The insolubility of spider silk in 8M urea, 50% lithium bromide, and 1%
sodium dodecyl sulfate (Table 1) implies that hydrogen bonding may not be the
only mechanism involved in intra-sheet associations between silk molecules,
(Seifter and Gallup 1966). This suggests that specific bonding mechanisms which
may hold the structure of the fibroin together are unaffected by this treatment.
Shaw (1964) and Lucas (1966) have conjectured on the nature of silk intra-sheet
bonding, but specific structural and chemical information is still lacking. The
absence of cysteine and methionine in the composition of N. clavipes dragline silk
seems to negate their possible role in the cross-linking of the silk chains. More
consistent conclusions are offered by Seifter and Gallup (1966), who state that the
structure of silk fibroins may consist of multiple protein regions joined by very
specific chemical cross-linkages, although the association between individual silk
molecules probably involves both covalent and non-covalent interactions.

The amino acid composition of N. clavipes dragline silk depicted in Table 2
shows a uniform trend in chemical composition. In order to determine whether
these trends were actually uniform in nature, each spider was silked on three
separate occasions as previously described and analyzed in triplicate to yield 9
determinations per spider species. Examination of the data from samples taken
from N. clavipes show distinct, uniform trends in chemical composition. A wide
variation in MaAS amino acid composition was previously reported by Work and
Young (1987). It was our conclusion that the lack of variability in the present
study was due to the use of extremely sensitive and well defined analytical
techniques, high quality instrumentation and the absence of contamination by
other silks (e.g.. Minor amp nil ate gland silk). It was therefore concluded that the
data illustrates substantial continuity in the chemical composition of major
ampullate gland silk from N. clavipes.

Table 5 shows the differences in amino acid composition between B . mori silk
fibroin (cocoon) and N. clavipes silk fibroin (MaAS). It can be observed that the
composition of the two types of silks differ not only in relative percentages of
individual residues, but also in residues present/ absent. Two features of the

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Table 5. — Comparative data on Bombyx mori and Nephila clavipes silk fibroins. Data on B. mori
from Lucas et al. (1955).

Amino acid

Bombyx mori

Nephila clavipes (reeled)

Gly

44.1

37.1

Ala

29.7

21.2

Ser

12.4

4.5

Tyr, Phe

7.5

10.2

Leu, lie, Val, Asx, Glx

3.6

11.7

Thr

1.2

1.7

Arg

1.5

7.6

Trp

0.5

N/A

Pro

4.5

His, Cys, Lys

1.0

TOTAL

100.0

Res, short chain (SC)

86.2

62.2

Res, long chain (LC)

13.8

29.8

Ratio (LC/SC)

0.16

0.48

analysis are worth noting; (1) the high percentage of short-chain residues in
Bombyx fibroin (86.2%) versus Nephila fibroin (62.2%), and (2) the 3-fold
increase in ratio of LC/SC residues in Nephila fibroin (0.16 vs 0.48). These
findings may be critical in determining the relative ratios of crystalline-to-
amorphous regions in silk, although more empirical evidence is required.

It is routinely believed that in the fibroin of the silkworm B. mori there is a
consensus sequence of (Gly-X-Gly-X-Gly-X)n, where X is alanine or serine,
although researchers have generally differed upon the exact amino acid
composition of Bombyx silk (Lucas et al. 1960; Iizuka 1970; Komatzu 1979;
Nadiger et al. 1985). Dickerson and Geis (1969) postulated that the glycine side
chains (— H) align themselves opposite alanine (— C^FL) or serine (— C^LLO^H)
side chains to conform to the anti-parallel /3-pleated sheet structural model of
Pauling and Corey (1953). It should be understood that this applies to the
crystalline region of Bombyx silk as determined by x-ray diffraction patterns
(Iizuka 1965). The high proportion of short side chain amino acids (62%) in the
MaAS make it more conceivable for the fiber to attain the conformational
structure of the anti-parallel /Tpleated sheet. This predicted condition is purely
theoretical because the ratios of crystalline-to-amorphous regions in both B. mori
cocoon silk and N. clavipes dragline silk are currently unknown. One can assume
that the relative amounts of crystalline and amorphous regions may be
determined relative to their physio/chemical properities and their effect on the
protein fiber. These assumptions are substantiated by the early work on fibers by
Lucas et al. (1955). Interestingly enough we may equate conclusions about
physical properties in which small differences induced in the chemical
composition of synthetic man-made fibers (e.g.. Nylon, Kevlar) translate into
significant changes in the physio/chemical properties of the fiber.

The results depicted in table 4 show uniform trends, but clear differences are
observed under closer scrutiny. Closer similarities are seen between Nephila and
Argiope than between Argiope and Neoscona which are from the same family.
Although these differences may be ecologically and/or phylogenetically-based.
Further analyses of additional species is needed.

LOMBARDI & KAPLAN— AMINO ACIDS IN NEPHILA CLAVIPES SILK

305

The identification of silk gene-related DNA sequences in recombinant
organisms may aid in the understanding of the interaction between chemical
composition/ protein sequence and the exceptional physical properties conferred
upon the protein fiber. Studies at the genetic, DNA/ protein sequence, and
transcriptional/ translational control levels will further the understanding of the
structure/ function relationships of naturally occuring fibers.

ACKNOWLEDGMENTS

The technical guidance of Ted Tanhauser and Bod Sherwood, Cornell
University for solubilization, hydrolysis, and analysis is appreciated. The authors
also express their appreciation to Mark Stowe and Angela Choate, University of
Florida, Gainesville, FLA for supplying unlimited quantities of spiders. We thank
Scott Stockwell who provided helpful comments and suggestions on early drafts
of this manuscript.

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Manuscript received January 1990, revised April 1990.

Zeh, J. A. and D. W. Zeh. 1990. Cooperative foraging for large prey by Paratemnus elongatus
(Pseudoscorpionida, Atemnidae). J. Arachnol., 18:307-311.

COOPERATIVE FORAGING FOR
LARGE PREY BY PARATEMNUS ELONGATUS
(PSEUDOSCORPIONIDA, ATEMNIDAE)

Jeanne A. Zeh and David W. Zeh

Smithsonian Tropical Research Institute
APO Miami 34002-0011, USA

Apartado 2072
Balboa, Republic of Panama

ABSTRACT

Interrelatedness among colony members and predation competence through cooperative foraging
have been proposed as factors which act to maintain an atypically high level of social organization in
the pseudoscorpion, Paratemnus elongatus. In this paper we report on two sets of field observations
consistent with these hypotheses: 1) female-bias in sex ratio, and 2) the ability of P. elongatus to
capture unusually large, heavily-armored prey. Cooperative foraging behavior enables this
pseudoscorpion to exploit ant prey ( Cephalotes atratus ) thirty times it own mass.

INTRODUCTION

Paratemnus elongatus (Banks) exhibits the highest level of social organization
known among pseudoscorpions (Brach 1978). In the laboratory, immature instars
communally spin and occupy silken nests used for molting, and adults and
penultimate instars (tritonymphs) engage in cooperative predation (Brach 1978).
These social behaviors are of particular evolutionary interest since pseudo-
scorpions are predominantly solitary and often intraspecifically aggressive
(Weygoldt 1969; Zeh 1987). In fact, in other pseudoscorpions species, e.g.,
Dinocheirus arizonensis (Banks) and Parachelifer hubbardi (Banks) from
Arizona, and Cordylochernes scorpioides (L.) and Semeiochernes armiger
(Balzan) from Panama, we have observed numerous instances of cannibalism
involving adults and nymphs preying upon same or earlier stage instars in both
field and laboratory situations (personal observations).

Brach (1978) speculated that the evolution of cooperative behavior in P.
elongatus was linked to both interrelatedness among colony members and
enhanced foraging proficiency resulting from group predation. Here we provide
the first quantitative data on colony composition and sex ratio in P. elongatus
and describe field observations of cooperative foraging behavior which lend
support to Brach’s hypothesis.

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METHODS

Between April 1988 and December 1989 we collected R elongatus from beneath
the bark of live or recently fallen trees, including Miconia argeniea , Bursera
simaruba , and Tetrathylacium johansenii. The pseudoscorpions generally occurred
in discrete clusters (colonies) beneath sections of bark. Collections were made by
brushing whole colonies into a plastic bag held firmly against the trank of the
tree. We collected them from Cerro Luisa, Gamboa, Carnino de Cruces Trail,
Barro Colorado Island, and Gigante Peninsula, all of which lie in tropical moist
forest of the former Canal Zone, Republic of Panama. Descriptive statistics on
colony composition were computed using SAS (SAS Institute, Inc. 1988). In
order to test for departure from 1:1 sex ratio, we treated each colony, not
individual pseudoscorpions, as a replicate. A paired /-test of the number of
female minus male individuals in each colony was carried out on log-transformed
data to equalize variance. In addition, 20 first instars (protonymphs) from three
colonies were reared to adults in the laboratory to assess the correspondence
between primary and adult sex ratio.

Voucher specimens of the pseudoscorpion have been deposited with W. M.
Muchmore of the University of Rochester and with V. Mahnert of the Museum.
d’Histoire naturelle, Switzerland. Both taxonomists have indicated that species
identification of this pseudoscorpion is tentative. Paratemnus elongatus , which
has been recorded from southeastern U.S.A., Central America, Dominica, and
northern South America, is very similar morphologically to R nidificator (Balzan)
from Paraguay and P. minor (Balzan) from Brazil, and Mahnert believes that
further study may show the three species to be synonymous (personal
communication).

Observations and photographs of foraging behavior in P. elongatus were taken
over a two-week period in April and May 1988. Seven colonies of
pseudoscorpions had become naturally established over a 60 m section of chain-
link fence immediately adjacent to second-growth forest in Gamboa, Panama.
The colonies were located beneath gaps in metal sleeves connecting upright fence
posts to the top horizontal bar. A common prey item of the pseudoscorpions was
Cephalotes atratus (L.). Voucher specimens of the ant have been deposited with
D. Quintero of the University of Panama.

A sample of ants and pseudoscorpions was dried at 50 °C to constant weight
(Cairn 28 Automatic Eiectrobalaeee) in order to compare the relative mass of
prey and predator.

RESULTS AND DISCUSSION

Colony composition. — Total number of individuals per collection varied
between one and 53 with a mean (± SE) of 11.3 ± 2.3 ( N = 23 collections).
When categorized by life stage and adult sex, the mean numbers of individuals
per collection are as follows: males = 1.43 ± 0.26; females : ; 3.22 ± 0.62;
tritonymphs = 3.26 ± 0.90; deutonymphs = 2.70 ± 0.82; protonymphs = 0.65 ±
0.33, The most striking pattern which emerged was the strong female-bias in
colony sex ratio, with a mean proportion of males (pm) = 0.31 + 0.11. This
departure from a 1:1 sex ratio is highly significant statistically (t — 2.56, P =

ZEH & ZEH— COOPERATIVE FORAGING IN PARATEMNUS

309

0.009). Of the 20 individuals reared from protonymphs in the laboratory, there
were 12 females, six males, and two deaths (pm = 0.33). Taken together these data
suggest that bias in the primary sex ratio and not sexual differences in mortality
are the causes of the skewed adult sex ratio.

Population genetic models predict female-biased sex ratios in inbred
populations since an excess of females acts to reduce local mate competition, i.e.,
competition for mates between related male offspring (see Hamilton 1967).
Comparative data on a variety of species demonstrate a strong empirical link
between inbreeding and sex ratio bias (Bulmer 1986). Thus our findings are
consistent with (but do not prove) the hypothesis of interrelatedness among
colony members. We are currently developing electrophoretic methods in order to
more directly assess relatedness levels in this species.

Field observations of predation. — Corpses of medium- to large-sized insects
(beetles, millipedes, and ants) were found with their appendages lodged within the
entrances of the pseudoscorpion colonies. These included six specimens of the
large, heavily-sclerotized cephalotine ant, Cephalotes atratus (see Corn 1980). On
two occasions (1700 hours, 30 April 1988; 1730 hours, 2 May 1988), successful
capture of and predation on live C. atratus were observed. With pedipalps
extended, adult P. elongatus were assembled along the entrance of the colony to
form a nearly continuous battery of chelae. As the ant walked across the colony
entrance, several pseudoscorpions used their chelae to clamp onto the ant’s
forelegs (Fig. 1). The pseudoscorpions then pulled back into the colony, pinning
the ant against the entrance. Tritonymphs converged on the ant within 60 s of
capture and began inserting their chelicerae into articulations of the leg segments.
Except for brief excursions, the pseudoscorpions remained at or within the nest
entrance for at least 1 h after capture. After 3 h, tritonymphs were observed
outside the entrance feeding on the abdomen of the ant. Comparative dry weight
data illustrate the magnitude of the size discrepancy between prey and predator —
the ants outweigh the pseudoscorpions by a factor of 30 (mean dry weight in mg:
P elongatus = 0.55 ± 0.03, N= 11; C. atratus = 16.08 ± 0.75, N — 12).

Observations of staged encounters made on three colonies suggest that
cooperative effort is important in enabling Paratemnus to dispatch large prey.
For each colony, a single live ant was deposited five times at the nest entrance
(different ant used for each colony). Ants walking over the colony entrance
escaped capture when only one pseudoscorpion managed to grasp a leg (5 of the
15 trials). Successful captures (4 of 15 trials) minimally involved three adult
Paratemnus grasping the ant within 5 s of the first individual’s attachment. In
addition, ants which we forcefully dislodged from pseudoscorpions were still alive
and mobile 10 min after capture, indicating that pseudoscorpions must restrain
the ant for a relatively long period in order to kill it. In the remaining six trials,
no pseudoscorpion was successful in grasping the leg of the ant.

Interesting observations of Paratemnus and Cephalotes have been recorded by
M. L. Corn working in Colombia. Corn was perplexed by observations of
Paratemnus sp. feeding on recently dead C atratus since in other contexts this
heavily-armored ant appeared to be impregnable to the attacks of predators. She
observed C. atratus workers emerging relatively unscathed from columns of
raiding army ants ( Labidus sp.) (personal communication to W. B. Muchmore).

The potential significance of cooperative predation in P. elongatus is perhaps
best illustrated by a quote from Oliveira and Sazima (1985): “Ants outnumber in

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Figure 1. — Predation on a Cephalotes atratus worker by a colony of the pseudoscorpion
Paratemnus elongatus.

individuals all other terrestrial animals and, although they represent a significant
food resource, few predators regularly feed on them.” We suggest that the ability
to dispatch large prey through cooperative predation has been an important
factor in the ecological success of this very abundant (Hoff 1964) and widely-
distributed pseudoscorpion.

ACKNOWLEDGMENTS

We thank G. McPherson and D. M. Windsor for tree species identification, D.
Quintero for identifying the C. atratus , N. Smythe for logistic support, Y.
Gamarra for weighing specimens, and W. B. Muchmore and V. Mahnert for
identifying the Paratemnus. We especially thank Bill Muchmore for copies of
correspondence with M. L. Corn. This research benefited from discussions with
W. G. Eberhard, W. D. Hamilton, and M. J. West-Eberhard. Both authors
gratefully acknowledge fellowship support from the Smithsonian Tropical
Research Institute. We also thank the Panamanian Institute Nacional de
Recursos Naturales Renovables (INRENARE) for permission to carry out this
research (permit number 16-87).

LITERATURE CITED

Brach, V. 1978. Social behavior in the pseudoscorpion Paratemnus elongatus (Banks)
(Pseudoscorpionida: Atemnidae). Insectes Sociaux, 25:3-1 1.

Bulmer, M. 1986. Sex ratios in geographically structured populations. Trends Ecol. Evol., 1:35-38.

ZEH & ZEH — COOPERATIVE FORAGING IN PARATEMNUS

311

Corn, M. L. 1980. Polymorphism and polyethism in the neotropical ant Cephalotes atratus (L.).
Insectes Sociaux, 27:29-42.

Hamilton, W. D. 1967. Extraordinary sex ratios. Science, 156:477-488.

Hoff, C. C. 1964. Atemnid and cheliferid pseudoscorpions, chiefly from Florida. Amer. Mus.
Novitates, 2198: 1-43.

Oliveira, P. S. and I. Sazima. 1985. Ant-hunting behaviour in spiders with emphasis on Strophius
nigricans (Thomisidae). Bull. Br. Arachnol., Soc., 6:309-312.

SAS Institute, Inc. 1988. SAS/STAT user’s guide, release 6.03 edition. Cary, N.C., U.S.A.

Weygoldt, P. 1969. The biology of pseudoscorpions. Harvard University Press, Cambridge. 145 pp.

Zeh, D. W. 1987. Aggression, density and sexual dimorphism in chernetid pseudoscorpions
(Arachnida: Pseudoscorpionida). Evolution, 41 : 1072-1087.

Manuscript received January 1990, revised May 1990.

Porter, A. H. and E. M. Jakob. 1990. Allozyme variation in the introduced spider, Holocnemus
pluchei ( Araneae, Pholcidae) in California. J. Arachnol., 18:313-319.

ALLOZYME VARIATION IN THE INTRODUCED SPIDER
HOLOCNEMUS PLUCHEI (ARANEAE, PHOLCIDAE)
IN CALIFORNIA

Adam H. Porter

Department of Zoology
University of California
Davis, California 95616 USA

and

Elizabeth M. Jakob1

Animal Behavior Graduate Group
University of California
Davis, California 95616 USA

ABSTRACT

Ten electrophoretic loci were scored for five California populations of the pholcid spider,
Holocnemus pluchei. Two loci were variable, with two allelles present at each. Genetic differentiation
among populations was weak (mean Fst = 0.1 16; Nei’s unbiased D < 0.015); this may be attributable
to the recency of introduction and opportunities for gene flow afforded by the affinity of these spiders
for urban habitats. A single population of the ecologically similar pholcid Pholcus phalangioides
differed from Holocnemus at seven of 10 loci.

INTRODUCTION

The Mediterranean pholcid spider Holocnemus pluchei (Scopoli) was recently
introduced into the United States. The oldest reliable North American record
known to us is an observation by W. R. Icenogle in Sutter Co., California in 1974
(S. Frommer pers. comm.). It is quite possible that Holocnemus was introduced
into the state prior to 1974 but escaped attention because it superficially
resembles another pholcid, Pholcus phalangioides (Fuesslin). In California,
Holocnemus occurs in high densities below 500 m elevation in cities and towns in
southern California and in the Central Valley. It is particularly common around
buildings, and liable to be transported passively in truck and railroad cargo. We
have seen small colonies as far east as Las Cruces, New Mexico.

Jakob and Dingle (1990) found statistically significant differences in
development time and body size among broods of H. pulchei reared under
identical conditions. Spiders in the field also show a wide range of phenotypic
behavioral variation, including solitary living and group living (Jakob 1989,
1991). Here we report the genetic population structure of Holocnemus in
California; the elucidation of genetic differentiation within and among

1 To whom reprint requests should be sent.

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Figure 1. — Collecting localities for Holocnemus pluchei in California.

populations provides an important context in which to study evolutionary
processes. Because material was readily available, we also report the genetic
distance between Holocnemus and Pholcus phalangioides , a phenotypically and
ecologically similar spider also introduced from Europe.

METHODS

The Holocnemus populations surveyed are shown in Fig. 1; these were
collected from university campuses and apartment buildings at five sites in
California. Pholcus were collected in Wisconsin and mailed to Davis. In addition,
Holocnemus broods reared from field collected egg sacs were assayed at
polymorphic loci for evidence of Mendelian ratios, as an indication that the
electromorphs represented heritable variants. All spiders were starved for one
week prior to analysis to ensure that prey enzymes would be fully digested.

We used the electrophoresis protocol of Ayala et al. (1972). Thirteen enzyme
systems were surveyed (Table 1). The computer program BIOSYS-1 (Swofford

PORTER & JAKOB— ALLOZYME VARIATION IN HOLOCNEMUS

315

Table 1. — Enzyme systems surveyed, with Enzyme Commission Numbers.

Enzyme

Abbreviation

E.C. #

Adenylate kinase

2.7. 4.7

Aldolase

ALDO

4.1.2.13

Fumarase

FUM

4.2. 1.2

Glutamic-oxaloacetic transaminase

GOT

2.6. 1.1

Glyceraldehyde-3-phosphate dehydrogenase

GAPDH

1.2.1.12

a-Glycerophosphate dehydrogenase

a-GPD

1. 1.1.8

Hexokinase

2.7.1. 1

Isocitrate dehydrogenase

IDH

1.1.1.42

Malate dehydrogenase

MDH

1.1.1.37

Malic enzyme

1 . 1 . 1 .40

Phosphoglucose isomerase

PGI

5.3. 1.9

Phosphoglucomutase

PGM

2.7.5. 1

Superoxide dismutase

SOD

1.15.1.1

and Selander 1981) was used for the genetic analyses, x2 procedures were used to
test for deviations from Hardy-Weinberg expectations. Genetic variability scores
(heterozygosity and polymorphic loci) provide an estimate of the degree of
variation available for evolutionary change in populations. We report two
standard heterozygosity scores: observed heterozygosity (H0fo) is the proportion of
loci found to be heterozygous by direct observation of genotypic frequencies;
expected heterozygosity (HexP) is the proportion of heterozygotes calculated from
allelic frequencies under the expectation of Hardy- Weinberg ratios of genotypic
frequencies. We also report the percent of loci we observed to be polymorphic (P)
in each population, and provide a rough comparison of these statistics to those of
other spiders.

Divergence among populations was analyzed using Nei’s (1978) unbiased
genetic distance, which adjusts for small and variable sample sizes, and also using
Wright’s (1931) Fst. Fst is an estimate of the component of overall genetic
variance attributable to among-population effects, standardized by the total
genetic variance available. Fst can be related directly to important homogenizing
and differentiating influences of gene flow, natural selection, and genetic drift.
Differentiation is strong when Fst > 0.33: above this level, the effects of
homogenizing factors (gene flow and balancing selection) become relatively
unimportant in determining differences among populations (see Wright [1978]
and Slatkin [1985] for discussion). The mathematical definitions of the population
genetic parameters reported here can be found in any introductory population
genetics textbook (e.g., Hedrick 1985).

RESULTS AND DISCUSSION

We were able to stain and reliably score 10 loci (GAPDH, GOT-1, GOT-2, HK,
IDH-1, MDH-1, MDH-2, PGI, PGM, and 6-PGD; where “1” is the fastest locus
migrating in the cathodal direction). In Holocnemus , two of these loci were
variable (GOT-1, PGI) with two alleles each; the remainder were fixed for the
same allele in all populations. Allelic frequencies for the variable loci are given in
Table 2; genotypic frequencies did not deviate from Hardy-Weinberg
expectations. The reared broods assayed for GOT-1 and PGI showed Mendelian

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Table 2. — Animals sampled (TV) and allelic frequencies for variable loci in Holocnemus pluchei
populations. Allele F migrates fast cathodally, S is slower.

Population

Locus and allele

GOT-1

PGI

Davis

0.603

0.397

0.879

0.121

Fresno

0.684

0.316

0.975

0.025

Bakersfield

0.947

0.053

0.765

0.235

Newhall

1.000

0.000

0.893

0.107

Riverside

0.816

0.184

0.971

0.029

ratios in most cases where variability was present (Table 3). However, Brood 1
deviated from Mendelian ratios at GOT-1; this may have been due to multiple
mating with males of different GOT-1 genotypes, but if so, the genotypic ratio at
PGI indicates that all the fathers were PGI heterozygotes. No field data
concerning the frequency of multiple mating are available.

Genetic variability scores for all populations are shown in Table 4. Genetic
distances between Holocnemus populations are quite low (Table 5), and analysis
using Fst indicates that the relative genetic differentiation among populations is
biologically minor (GOT-1: Fst = 0.148; PGI: Fst — 0.063; mean Fst = 0.116). As
a comparison, mean Fst = 0.009 among sample populations of the eastern North
American monarch butterfly (Fanes and Koehn 1978), which is essentially
panmictic; Fst = 0.705 among sample populations of a plethodontid salamander
(Wake and Yanev 1986). The genetic distance between Pholcus and Holocnemus
is high (Table 5): these taxa show fixed differences at seven of the ten loci scored
(GAPDH, GOT-2, HK, IDH-1, MDH-1, PGI, 6-PGD), suggesting a very old
divergence between these ecologically rather similar species.

While genetic variability in Holocnemus pluchei is low relative to most
invertebrate species examined (Nevo 1978), it remains within the range reported
in other spiders. Different heterozygosity parameters used in the arachnological
literature makes comparison difficult, permitting only a rough sense of the
reported range of variability: heterozygosities (H0&s and He*P) from the literature
range from a low of 0.017 in Anelosimus eximius (He*P; Smith 1986) to a high of
0.094 in Araneus ventricosus (H0&s; Manchenko 1981). The degree of

Table 3. — Genotypic frequencies for variable loci in broods reared from wild-collected females. Only
brood 6 at GOT-1 differs significantly from Mendelian expectations (P< 0.0001; see text).

1989 brood number

Genotype

GOT-1

PGI

PORTER & JAKOB ALLOZYME VARIATION IN HOLOCNEMUS

317

Table 4. — Genetic variability scores for all populations. A = mean number of alleles per locus; H0&s
= observed proportion of heterozygotes; Wexp = proportion of heterozygotes calculated from Hardy-
Weinberg proportions; P = percent of loci polymorphic, with more than one allele detected. Standard
errors in parentheses.

Population

Ho6s

Hexp

Davis

1.2 (0.1)

0.083 (0.061)

0.070 (0.051)

20.0

Fresno

1.2 (0.1)

0.068 (0.063)

0.049 (0.044)

20.0

Bakersfield

1.2 (0.1)

0.046 (0.036)

0.047 (0.037)

20.0

Newhall

1.1 (0.1)

0.021 (0.021)

0.020 (0.020)

10.0

Riverside

1.2 (0.1)

0.043 (0.037)

0.037 (0.031)

20.0

Wisconsin ( Pholcus )

1.0 (0.0)

0.000 (0.000)

polymorphism (assessed as the percent of loci with more than one electromorph
observed) ranges from a low of 3.9% in one population of A. eximius (Smith
1986) to a high of 33% in an A. ventricosus population (Manchenko 1981). We
omit the high variability scores calculated from Pennington’s (1979) genotypic
frequency data because he assayed only polymorphic loci. Note however that it is
not possible to generalize about variability across all spiders because most
previous work concerns spiders with unusual social structures that may well
influence patterns of genetic variability (see also Cesaroni et al. 1981). The high
genetic similarity among Holocnemus populations may have up to three
contributing factors. If natural selection on these loci is negligible, genetic drift
alone countered by a gene exchange rate of approximately 2 individuals per
generation will explain the observed level of population differentiation (using
Wright’s [1931] formulation Nm ~ (1/Fst ~ l)/4, where Nm is the rate of gene
exchange among populations in an island model of genetic population structure;
see also Slatkin and Barton [1989]). This level of gene flow is well within the
range expected from the spiders’ affinity for urban and suburban habitats.
However, selection for balanced polymorphisms at variable loci can also promote
similarity. The recency of the Holocnemus introduction in California may
promote similarity as well: genetic drift is a function of population size, and the
large population sizes in California may not have had time to fully differentiate.
These latter factors, depending on their importance, will correspondingly reduce
the estimate of gene flow required to explain present levels of differentation.
Repetition of this study after 10-15 years, and a study of European populations,
would help to determine the relative importance of these factors.

Holocnemus is also unusual in having been recently introduced in California,
and its low variability scores are perhaps to be expected: low heterozygosity in
founder populations is well known (e.g., Harrison et al. 1983). Indeed, the

Table 5. — Pairwise
distance.

genetic

distances between

populations

using Nei’s (1978)

unbiased genetic

Population

Davis

Fresno (F)

0.000

Bakersfield (B)

0.013

0.011

Newhall (N)

0.015

0.010

0.001

Riverside (R)

0.004

0.001

0.005

0.003

Pholcus

1.309

1.290

1.197

1.194

1.249

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THE JOURNAL OF ARACHNOLOGY

maximum of two alleles per locus found in this survey suggests that the original
California propagule may have been as small as a single gravid female. The
complete lack of genetic variability in the single Pholcus population may not be
representative of the species as a whole, because this sample was collected from a
small, isolated population.

Given the relatively low genetic variability scores and the recency of
introduction into California, the differences in life history traits among families
reared under identical conditions (Jakob 1989; Jakob and Dingle 1990) are
striking. Such variation may result from genetic differences among families, but
may also arise in part from differences in the maternal environment during egg
maturation — egg size, for example, may vary depending on the mother’s foraging
success. Maternal effects can be quantified through more elaborate experimental
designs. The wide range of behavior expressed during H. pluchei social
interactions in the field (Jakob 1989, 1991) may be maintained in the population
by genetic polymorphisms in loci which regulate such behaviors deterministically,
or a “general purpose” genotype shared by all members of the population which
permits the spiders to behave flexibly. To the extent that the low level of genetic
variability shown in this study is representative of the genome, the second
alternative seems most likely.

The low variability in the loci studied does not bode well for the use of
electrophoretic data for in situ paternity analysis or other fine-grained field
studies in Holocnemus (c.f., Jakob 1989). However, this technique could be used
under laboratory conditions to determine, for example, whether spiderlings
joining groups prefer closely related individuals.

ACKNOWLEDGMENTS

We thank H. Dingle, F. J. Ayala, and H. B. Shaffer for the use of laboratory
facilities; H. Dingle, P. S. Ward, J. Stamps, M. G. Ramirez, and Y. D. Lubin for
comments on the manuscript; S. Frommer, D. Ubick and M. Moody for
Holocnemus identification and unpublished information on its introduction; T.
Reichert for the Pholcus sample; and A. Lung, D. Cook, and N. Gregory for help
with rearing. Jastro-Shields Scholarships to both authors from the University of
California at Davis and a Sigma Xi Grant-in-Aid of Research to EMJ covered
electrophoresis and travel costs.

LITERATURE CITED

Ayala, F. J., J. R. Powell, M. L. Tracey, C. A. Mourao and S. Perez-Salas. 1972. Enzyme variability
in the Drosophila willistoni group. IV. Genetic variation in natural populations of Drosphila
willistoni. Genetics, 70:1 13-139.

Cesaroni, D., G. Allegrucci, M. Caccone, M. C. Sbordoni, E. De Matthaeis, M. Di Rao and B.
Sbordoni. 1981. Genetic variability and divergence between populations and species of Nesticus
cave spiders. Genetica, 56:81-92.

Eanes, W. F., and R. K. Koehn. 1978. An analysis of genetic structure in the monarch butterfly,
Danaus plexippus L. Evolution, 32:784-797.

Harrison, R. G., S. F. Wintermeyer and T. M. Odell. 1983. Patterns of genetic variation within and
among gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae) populations. Ann. Entomol.
Soc. America, 76:652-656.

Hedrick, P. W. 1985. Genetics of Populations. Jones & Bartlett, Boston. 629 pp.

PORTER & JAKOB— ALLOZYME VARIATION IN HOLOCNEMUS

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Jakob, E. M. 1989. Costs and benefits of group living in a pholcid spider ( Holocnemus pluchei). PhD
Thesis, University of California at Davis, Davis, California. 88 pp.

Jakob, E. M. 1991. Costs and benefits of group living for pholcid spiders: losing food, saving silk.
Animal Behaviour, in press.

Jakob, E. M. and H. Dingle. 1990. Food level and life history in a pholcid spider. Psyche, in press.

Manchenko, G. P. 1981. Allozymic variation in Araneus ventricosus (Arachnida, Aranei). Isozyme
Bull., 14:78.

Nei, M. 1978. Estimation of average heterozygosity and genetic distance from a small number of
individuals. Genetics, 89:583-590.

Nevo, E. 1978. Genetic variation in natural populations: patterns and theory. Theor. Pop. Bio.,
13:121-177.

Pennington, B. J. 1979. Enzyme genetics in taxonomy: diagnostic enzyme loci in the spider genus
Meta . Bull. Br. Arachnoh Soc., 4:377-392.

Slatkin, M. 1985. Gene flow and the geographic structure of natural populations. Science, 236:787-
792.

Slatkin, M. and N. H. Barton. 1989. A comparison of three indirect methods for estimating average
levels of gene flow. Evolution, 43:1349-1368.

Smith, D. R. R. 1986. Population genetics of Anelosimius eximius (Araneae, Theridiidae). J.
Arachnoh, 14:201-217.

Swofford, D. L. and R. B. Selander. 1981. A computer program for the analysis of allelic variation in
genetics. J. He red., 72:281-283.

Wake, D. B. and K. P. Yanev. 1986. Geographic variation in allozymes in a “ring species,” the
plethodontid salamander Ensatina eschschoitzii in southern California. Evolution, 40:702-715.

Wright, S. 1931. Evolution in Meedelian populations. Genetics, 16:97-159.

Wright, S. 1978. Evolution and the Genetics of Populations. Volume 4. Variability Within and Among
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Manuscript received January 1990 , revised May 1990.

Fincke, O. M., L. Higgins and E. Rojas. 1990. Parasitism of Nephila clavipes (Araneae,
Tetragnathidae) by an ichneumonid (Hymenoptera, Polyspinctini) in Panama. J. Arachnol.,
18:321-329.

PARASITISM OF NEPHILA CLAVIPES
(ARANEAE, TETRAGNATHIDAE) BY AN ICHNEUMONID
(HYMENOPTERA, POLYSPHINCTINI) IN PANAMA

Ola M. Fincke1

Smithsonian Tropical Research Institute
APO 34002, Miami, USA

and

Linden Higgins2

Department of Zoology, University of Texas
Austin, Texas 78712 USA

and

Edgar Rojas

Departamento de Biologia, Universidad de Costa Rica
Ciudad Universitaria, Costa Rica

ABSTRACT

An apparent outbreak of Hymenoepimecis sp., a heretofore unknown ectoparasite of the giant orb
weaver, Nephila clavipes is documented in Panama during 1984-1985. Parasitism was highest (25-30%)
among intermediate-sized, juvenile female spiders. During the second year the wasps became less
discriminating in selecting host spiders. Female wasps were significantly larger than males, and the
size of the wasp ectoparasite was positively correlated with the size of the host spider. Although
intermediate-sized females that had males in their webs were less likely to be parasitized than such
females without males, results from an insectary experiment showed that male spiders did not prevent
an established wasp larva from killing its host.

INTRODUCTION

The Pimplinae is a diverse subfamily of Ichneumonid wasps, within which the
tribe Polysphinctini are ectoparasites of spiders. Currently there are no published
accounts of the biology of any neotropical Polysphinctine (Wahl pers. comm.;
Fitton et al. 1988), nor of their effect on the host population. In Panama we
witnessed high levels of parasitism by an undescribed polysphinctine wasp,
Hymenoepimecis sp., whose host was the golden orb weaver spider, Nephila
clavipes (L.). Herein we describe the life cycle of the parasitoid wasp, and
document the frequency of the parasitoid in the host population over a two-year
period.

Current addresses:

1 Department of Zoology, University of Oklahoma, Norman, Oklahoma 73019 USA

2 Centro de Ecologia, Universidad National de Mexico, Apartado Postal 70-275, Ciudad Universitaria,

C.P. 04510 Mexico

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MATERIALS AND METHODS

The study was conducted on Barro Colorado Island (hereafter designated BCI)
in the Republic of Panama. There, the lowland moist forest experiences a dry
season from January to May (see Leigh et al. 1982 for habitat description). The
host spider, Nephila clavipes , normally has two generations per year, with mature
adults peaking in early wet season and in late wet to early dry season (Lubin
1978; Vollrath 1980).

The frequency of Hymenoepimecis sp. on N. clavipes was measured during two
study periods that encompassed both dry and wet seasons in 2 consecutive years;
from March to August 1984, and from February to December 1985. In 1984 N.
clavipes was sampled by noting individuals encountered along roughly 1.5 km of
trails transecting mature forests, and in the clearings adjacent to these trails. We
marked the location of the web and measured the total length of the spider’s
cephalothorax-abdomen with calipers, recorded the number of males present in
the web, and noted the presence of any parasitoid eggs or larvae on the female
spider. Webs were checked on average of once every 3 days, until the spider could
no longer be found in its original spot, or until the end of the study period.

In 1985, spiders were checked weekly or bi-weekly along 2 km of trails on BCI
and the size of the spider was measured by the tibia-patella length. The
cephalothorax-abdomen length of female spiders was highly correlated with tibia-
patella length (r = 0.96, N = 21 females, P < 0.05). For comparisons between
years, we converted body length data to estimates of tibia-patella length using the
regression equation. To determine whether the outbreak was a localized
phenomenon, monthly surveys of N. clavipes over roughly the same length of
trail were conducted on the mainland penninsula of Gigante from February 1985
to February 1986.

The life cycle of the Hymenoepimecis sp. parasitoid was studied by maintaining
field collected, parasitized spiders in an outdoor insectary (2 X 2 X 2.5 m). The
spiders readily built webs and fed on small insects thrown into their webs. We
measured the length of the parasitoids daily, noting when the host spider died,
and when the larva pupated. The wasp pupae were removed from the webs and
kept individually in small screen vials. The size and sex of the emerging adult
wasps was recorded. Oviposition behavior and the reaction of female N. clavipes
to wasps was noted opportunistically in the field.

Juvenile females with male spiders in the web were parasitized less frequently
than were those in the presence of male spiders. To determine if this effect was a
consequence of the male’s behavior, one or two males were placed in the webs of
12 recently parasitized female spiders that were maintained in the insectary.
Interactions between the parasitoids and the male spiders were noted during
hour-long daily observation periods until the host spider was killed or the
parasitoid disappeared.

RESULTS

Frequency and distribution of the parasitoid. — Parasitism by Hymenoepimecis
sp. on N. clavipes in 1984 and 1985 is shown in Table 1. In both years, female
spiders of intermediate size (corresponding to instars 5-8) were disproportionately

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323

Table 1. — Occurrence of parasitism by Hymenoepimecis sp. and of males in the webs of female N.
clavipes of different sizes. For comparison of percentage of parasitism, 1984 samples were combined.
* = The smallest instars were not sampled in 1984.

Tibia-patella
length (mm)

Year

Parasitized

Females

with males

<0.4

1984 (BCI) *

1985 (BCI)

117

5.9

1985 (mainland)

>0.4 <0.7

1984 (BCI)

8.3

1985 (BCI)

9.9

1985 (mainland)

14.0

>0.7 <1.2

1984 (BCI)

113

25.0

1985 (BCI)

30.0

1985 (mainland)

14.6

>1.2

1984 (BCI)

112

1.0

1985 (BCI)

1.2

1985 (mainland)

parasitized. Most (68%) sexually mature adult N. clavipes females were found in
association with one or more males whereas only 32% of the intermediate-sized
females had males in their webs. However, only 4 of the 154 (3%) N. clavipes
females that had males in the web were parasitized (x2 = 8.4, df — 1, P < 0.05).
Of the 5-8th instar females (i.e., those most heavily parasitized), 69 of 341 (20%)
had males in the webs. Only three of these females (4%) were parasitized as
opposed to a 27% parasitism rate in the 272 females (27%) that lacked males (x2
= 12.8 df= 1, P < 0.05).

In 1985, the incidence of parasitism in the BCI sample was about twice that
found in the mainland sample of N. clavipes (Table 1). In this year on BCI, the
normal peak in abundance of mature females in December never materialized
(Higgins, unpubl.). Concomitantly, ovipositing wasps were less discriminating in
their selection of host spiders. Eleven juveniles too small to sex (<4 mm tibia-
patella length) and 3 of the 61 juvenile males censused were parasitized. Four
cases of double parasitism were also observed.

Lifecycle of Hymenoepimecis sp. — We do not know how Hymenoepimecis sp.
detects N. clavipes hosts. However, once the wasp located a potential host, it was
not always successful in parasitizing the spider. On three occasions female N.
clavipes were found off of the web (either in the leaf litter or on a lateral branch)
while the wasp rested at the web center. The spiders approached the web, plucked
it, and then dropped into the leaf litter. The wasps reacted by flying off of the
web, circling it, and then flying away. Two of these spiders were later found
parasitized. The third already had an early instar larva attached to it. We did not
witness interactions that led to a wasp successfully landing on a spider host.

Hymenoepimecis sp. appeared to temporarily paralyze its host. On one
occassion a female wasp was seen to sting a spider between the sternum and the
coxae (see also Nielson, 1935; Eason et al., 1967). Typically, a wasp sat on the
dorsal or dorsal-lateral side of the spider’s abdomen, grasping the posterior end
of the abdomen with her first pair of legs (Fig. 1). The wasp then moved her
ovipositor back and forth for up to 5 min before attaching a single egg the cuticle

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of the spider. Fifteen min after the wasp oviposited, the host spider had fully
recovered.

Within 24 h the eggs (N = 4) hatched into larvae roughly 1 mm in length. One
newly hatched larva was unable to attach itself to the spider an died within 24 h.
Although this female spider grew to maturity (at below average size), she retained
a scar on the abdomen where the egg had been attached. Wasp larvae grew slowly
for the first week, after which they increased rapidly in size (Figs. 2, 3).
Parasitized female N. davipes built increasingly irregular, reduced webs but
continued to feed up to 1-2 days before they died. By the end of 2 weeks the
larvae had completely sucked out their host, leaving only the exoskeleton which
dropped to the ground. Three of the 25 larvae maintained in the insectary

FINCKE, ET A L . — NEP HI LA PARASITISM

325

Figure 2. — Hymenoepimecis sp, larva at 7 days post-hatch, attached to a female N. clavipes.

disappeared after killing the host. Remaining larvae took 3-5 h to build golden,
spindle-shaped cocoons that hung conspicuously within the frame lines of the
host web (Fig. 4).

Hymenoepimecis sp. larvae failed to complete development if the host spider
was too small or if it had already been parasitized. All of the larvae on juvenile
males and on the small females (<4 mm tibia-patella length) that were brought
into the insectary failed to pupate before the spider died. In all four cases of
double parasitism, the larger, first-laid larvae was the only one of each pair to
survive (one of these larva ate the other). Two of the 22 pupae formed in the
insectary failed to emerge for unknown reasons. In the field, one pupa was eaten
by a kleptoparasitic spider (. Argyrodes ), and three were found crushed by heavy
rains.

Even though male Hymenoepimecis sp._ were smaller (X body length ± SE —
14.8 ± 0.1 mm, N= 6) than the females (X ± SE = 17.6 ± 0.1 mm, N= 11), the
time required to emerge after pupation did_ not differ significantly between the
sexes (X = 10.4 ± 0.7 days, N = 5 males; x4 11.0 ± 0.4, N = 11 females). The

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Figure 3. — Male N. clavipes touching a wasp larva as the larva feeds on a female N. clavipes.
Pupation occurred 2 days later.

total time from egg to adult was 27 and 28 days for the two female wasps for
which the date of oviposition was known (we lack similar data for males). Newly
emerged adult Hymenoepimecis sp. released in the insectary with large N. clavipes
females did not mate nor orient to any of the spiders.

In both years the sex ratio of emerging wasps was significantly biased towards
females (1984, 7 males: 13 females; 1985, 6 males: 12 females, P < 0.05, x2 tests).
There was a significant correlation between size of the host spider (tibia-patella
length) and body length of the emerging wasp (r = 0.91, 7V= 7, P< 0.05).

Effects of male N. clavipes on success of the parasitoid. — In the insectary
experiment, all of the 12 parasitized female spiders with male N. clavipes in their

FINCK.E, ET Ah —NEPH1LA PARASITISM

327

Figure 4. — Pupa of Hymenoepimecis sp. in the web of the dead host female N. clavipes.

webs were eventually killed by the parasitoids, of which all but one pupated
successfully. The one exception was a larva that, after killing its host, failed to
pupate before it was eaten by a second N. clavipes female that wandered onto the
web. Periodically a larva raised its anterior end to reposition its mouth on
another area of the spider’s abdomen. During such times, male N. clavipes
occasionally touched the larva (Fig. 3), but they never removed nor ate larvae.
We cannot rale out the possibility that males interfere with successful oviposition
by the adult wasps.

DISCUSSION

The fact that N. clavipes host spiders continued to build webs and feed for
nearly two weeks after being parasitized indicates that Hymenoepimecis sp.
conforms with other known polysphinctines in being koinobiotie (i.e., paralyzing
their hosts only temporarily) (Askew and Shaw 1986). Many temperate
polysphinctines overwinter as small instars on the spider host and develop over
several months during which the host spider molts. Hymenoepimecis sp.,
however, developed rapidly and killed the host before the spider molted. The
larva of some parasitoids may actively inhibit molting, but the only parasitized N.
clavipes that we observed molting did so after losing its parasitoid. Because newly
emerged female Hymenoepimecis sp. did not react to male wasps nor to potential

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host spiders, their ovaries are probably undeveloped. The two periods during
which we sampled N. clavipes in 1984 corresponded closely to the peaks of
subadults and early adults of the biannual generations (Lubin 1978; Vollrath
1983). Unless it uses more than one host (unlikely for a koinobiotic
polysphinctine, see Fitton et al. 1988), the wasp parasitoid must live at least 1-2
months in order to persist during periods of low juvenile female densities,
between January and March, and August and October.

Because Hymenoepimecis larva were rarely seen to disappear from the host
spider, we conclude that the observed size-specific parasitism did not result from
differential larval success after oviposition. At present we do not know if the
disproportional use of intermediate-sized spiders results from a choice preference
by ovipositing wasps (e.g., Eason et al. 1967; Fitton et al. 1988) or from the
superior ability of larger N. clavipes females to avoid ovipositing wasps. Although
mature females that had male spiders in their webs suffered disproportionately
less parasitism than did mature females without males, male N. clavipes did not
interfere with successful development of the parasitoid. Limitation of parasitism
of N. clavipes to intermediate size classes of the host spider provides one adaptive
advantage to small size in male N. clavipes. By being too small to nourish a larva
to pupation, males effectively escaped attack by the wasp. In this study, mature
males were never observed to be parasitized, and juvenile males were parasitized
only in late 1985, when large juvenile females were scarce.

Male Hymenoepimecis sp. were significantly smaller than females, and wasp
size was correlated with the size of the host spider (see also Jowyk and Smilowitz
1978; Samson 1984), suggesting that an ovipositing female can assess the relative
size of a potential host, and control the sex of her eggs (e.g., Cole 1981; Sandlan
1979b; Askew and Shaw 1986). Hymenoepimecis sp. females may assess host size
and/or the presence of ectoparasitic larva by moving the ovipositor over the
host’s body prior to egg-laying.

Although Hymenoepimecis sp. becomes a large and conspicuous ectoparasite
on N. clavipes , parasitism by these wasps has not previously been reported by
other researchers working with N. clavipes on BCI (Robinson and Robinson
1977; Vollrath pers. comm). Nor were the ectoparasitoids noticed during three
months in 1982, when N. clavipes webs were monitored as part of a study of
spider predation by damselflies on BCI (Fincke unpub.). On mainland Panama
where the density of N. clavipes was greater than on BCI, Vollrath (pers. comm.)
found parasitoids only rarely. The high level of parasitism we found during 1984-
1985 suggests that this was an uncommon outbreak of Hymenoepimecis. The
environmental and biological factors that normally control the density of
Hymenoepimecis sp. are unclear. In 1985 both the dry and the wet seasons were
dryer than average (D. Windsor 1990). Because pupae were sometimes found to
be killed by the heavy rains, the parasitoids may benefit from dry weather.
Parasitism in 1984 probably contributed to the decline of the BCI N. clavipes
population found in 1985 which was coupled with double parasitism and the use
of host spiders of sub-standard size.

ACKNOWLEDGMENTS

We are indebted to D. Wahl and V. K. Gupta for independently identifying the
ichneumonid wasp to genus, and to W. E. Eberhard, I. Gauld, M. Robinson, and

FINCKE, ET AL. — NEPHILA PARASITISM

329

an unidentified reviewer for comments on the manuscript. This research was
funded by an Exxon Corp. Fellowship to E R., by a Smithsonian Postdoctoral
Fellowship to O. M. F., and an NSF Doctoral Improvement grant to L. H

LITERATURE CITED

Askew, R. R. and M. R. Shaw. 1986. Parasitoid communities: their size, and development. Pp. 225-
264 In Insect Parasitoids. (J. K. Waage and D. Greathead, eds.). Academic Press, London.

Cole, L. R. 1981. A visible sign of fertilization action during oviposition by an ichneumonid wasp,
Itopiectis maculator. Anim. Behav., 29:299-300.

Eason, R., W. B. Peck and W. H. Whitcomb. 1967. Notes on spider parasites, including a reference
list. J. Kans. Entomol. Soc., 40:422-434.

Fittoe, M. G., M. R. Shaw and L D. Gauld. 1988. Pimpline Ichneumon-flies, Hymenoptera,
Icheeumonidae (Pimplinae). In Handbooks for the Identification of British Insects, Vol. 7, Part I
(P. C. Barnard and R. R. Askew, eds.). Royal Entomological Society, London.

Jowyk, E. A. and Z. Smilowitz. 1978. A comparison of growth and developmental rates of the
parasite Hyposter exiguoe reared from two instars of its host, Trichoplusia ni. Ann. Entomol. Soc.
Am., 71:467-472.

Leigh, E. G., A. S. Rand and D. M. Windsor. 1982. The ecology of a tropical forest: seasonal
rhythms and long term changes. Smithsonian, Washington, D.C.

Lubin, D. Y. 1978. Seasonal abundance and diversity of web-building spiders in relation to habitat
structure on Barro Colorado Island, Panama. J. Arachnol, 6:32-51.

Maneval, H. 1936. Nouvelles notes sur divers hymenopteres et lews larves. Rev. Fr. Entomol., 3:18-
32.

Nielson, E. 1928. The Biology of Spiders II. Levin and Munksgaard, Copenhagen.

Nielson, E. 1935. A third supplementary note upon the life histories of Polysphinctas. Entomol.
Meddel, 19:191-215.

Robinson, M. 1977. Associations between flies and spiders bibicommensalism and dipoparasitism.
Psyche, 84:150-157.

Robinson, M. and B. Robinson. 1981. Ecologia y comportamiento de algueas aranas fabricadoras de
redes en Panama: Argiope argentata, A. savignyi , Nephila davipes y Eriophora fuliginea (Araneae:
Araneidae), Rev. Med. Panama. 6:90-117.

Rypstra, L. A. 1981. The effect of kleptoparasitism on prey consumption and web relocation in a
Peruvian population of the spider Nephila davipes. Oikos, 37:179-182.

Samson, P. R. 1984. The biology of Roptrocerus xylophagorum (Hym.: Torymidae), with a note on
its taxonomic status. Entomophaga, 29:287-298.

Sandlan, K. 1979b. Sex ratio regulation in Coccygomimus turionella Linneaus (Hymenoptera:

Ichneumonidae) and its ecological implications. Ecological Entomol, 4:365-378.

Vol I rath, F. 1980. Male body size and fitness in the web building spider Nephila davipes. Z.
TierpsycfaoL, 53:61-78.

Vollrath, F. 1983. Relative and absolute growth in Nephila davipes (Arachnida: Araneae: Argiopidae).
Verhaltnis naturwissenschaft, 26:277-289.

Windsor, D. M. 1990. Climate and moisture variability in a tropical forest: long-term records from
Barro Colorado Island, Panama. Smithsonian Contributions to the Earth Sciences No. 9.

Manuscript received July 1989, revised May 1990 .

Yu, L. and J. A. Coddington. 1990. Ontogenetic changes in the spinning fields of Nuctenea cornuta
and Neoscona theisi (Araneae, Araneidae). J. Arachnol., 18:331-345.

ONTOGENETIC CHANGES IN THE SPINNING FIELDS
OF NUCTENEA CORNUTA AND NEOSCONA THEISI
(ARANEAE, ARANEIDAE)

Liuming Yu

Div. of Biological Sciences
University of Missouri
Columbia, Missouri 65211 USA

and

Jonathan A. Coddington

Department of Entomology
National Museum of Natural History
Smithsonian Institution, Washington, DC 20560 USA

ABSTRACT

The postembryonic development of spinning organs of Nuctenea cornuta (Clerck) and Neoscona
theisi (Walckenaer) (Araneae, Araneidae), was studied with SEM, emphasizing first appearance of,
and increase in, spigot and fusule complements. Our results suggest that these species may renew their
spinning fields by two distinct methods during their ontogeny: spigots may be merely molted in situ
like any other cuticular appendage; and/or spigots in one position are lost and “replaced” by an
apparently new spigot in a new position. Some or all of each class of fusule (aciniform and pyriform)
as well as major and minor ampullate spigots are replaced as well as merely molted. Flagelliform and
aggregate spigots seem to be merely molted, never replaced. Evidence for these modes of replacement
are the apparently vestigial spinning structures that persist from the previous instar, termed “nubbins”
in the case of spigots, and “tartipores” in the case of fusules, as well as patterns in the increase in
numbers of fusules and spigots. Spinneret ontogeny confirms Theridiidae and Tetragnathidae as
phylogenetically derived taxa relative to Araneidae.

INTRODUCTION

Previous work on spinnerets has concerned histology (see Kovoor 1987 for a
review), morphology (Glatz 1967, 1972, 1973; Mikulska 1966, 1967, 1969;
Wasowska 1966, 1967, 1970, 1973; Coddington 1989), and function (Peters 1983,
1984; Peters and Kovoor 1980). Relatively few studies, and none using scanning
electron microscopy, have described the ontogeny of spinning organs. Mikulska
(1966) compared the differences of spinning structures between the adults and
subadults of Nephila clavipes (L.) but did not know to which instar the subadults
belonged. Richter (1970a) presented a very similar work on Pardosa amentata
(Clerck). Glatz (1972, 1973) compared the spinning structures of first instar to
those of adults for several primitive spider groups. Opell (1982) described the
ontogeny of only the cribellum of Hyptiotes cavatus (Hentz). Works on the entire
postembryonic ontogeny were done by Kokocinski (1968) and Wasowska (1977).

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Kokocinski used light microscopy to study the changes in the number of external
spinning structures in Agelena labyrinthica (Clerck). Wasowska used light
microscopy to describe the postembryonic morphology of the spinning apparatus
in eight species belonging to seven families (Thomisidae, Lycosidae, Agelenidae,
Argyronetidae, Theridiidae, Amneidae, Tetragnathidae).

In this study we observed the morphology of each instar with SEM to record
detailed characters apparently missed by Kokocinski and Wasowska, who were
limited to light microscopy.

For ease of discussion we maintain in this paper the distinction between
fusules — multiple spigots serving either aciniform or pyriform glands, and
spigots — morphologically singular spigots per se. Araneid spiders have five types
of spigots (major ampullate, minor ampullate, cylindrical, flagelliform, aggregate)
and two types of fusules (piriform, aciniform). All adults have one pair each of
major ampullates, minor ampullates and flagelliforms; two pairs of aggregates,
and three pairs of cylindricals. The positions of spinning structures and the
topographies of adult spinnerets are diagrammed in Coddington (1989).

MATERIALS AND METHODS

Nuctenea cornuta (Clerck) and Neoscona theisi (Walckenaer) were studied.
Both species are widely distributed in China. The specimens were collected in
Wuhan City, China and reared from eggsacs by Jingzhao Zhao, Professor in the
Department of Biology, Hubei University. Specimens of each instar were
preserved in 75% ethanol. All specimens of one species are from the same egg sac.
The number of specimens we used for each instar are given in Table 1. Vouchers
are deposited in the National Museum of Natural History (USNM), Smithsonian
Institution.

The methods used to prepare specimens generally follow Coddington (1989).
The forceps squeeze was only used for third instar or older, as younger instars are
too fragile. Younger instars are cleaned and whole abdomens mounted; careful
adjustments are needed in the 100% ethanol fixing and mounting steps to ensure
visibility of PMS and PLS spinnerets. Ultrasonic cleaning times differed among
instars: adults ca. 60 s; fourth or fifth, ca. 30 s; third, ca. 20 s; second, 0-5 s. First
instars were mounted without ultrasonic cleaning because their small bodies are
easily broken.

Numbers of spigots and fusules in Table 1 are reported for one spinneret of
each pair; to calculate total spinning complements, double that number.
Occasionally we use this calculated total when discussing our results. When a
difference in the number between the two spinnerets was found, both spinnerets
of the pair were counted.

Our nomenclature for instars of spiders follows Andre and Jocque (1986). We
call the stage emerging from the egg the “first” instar, the one emerging from the
eggsac the “second” instar, and number succeeding instars consecutively.
Individuals of each species matured in either the sixth or the seventh instar. The
loss of either spigots or fusules can result in vestigial structures of scars in
subsequent instars. To distinguish them we call nubbins resulting from fusules
“tartipores” (based on comments in Kovoor (1986) who first noticed the
structures), and nubbins resulting from spigots we simply call nubbins. The
figures portray either right or left spinnerets, depending on the specimen used.

YU & CODDINGTON— ONTOGENETIC CHANGES IN SPINNING FIELDS

333

Abbreviations are: AC, aciniform; AG, aggregate; ALS, anterior lateral
spinnerets; CY, cylindrical; FL, flagelliform; MAP, major ampullate; mAP, minor
ampullate; Nc, Nuctenea cornuta ; Nt, Neoscona theisi , PI, piriform; PMS,
posterior median spinnerets; PLS, posterior lateral spinnerets; tart., tartipores.
Throughout the text, these abbreviations are intended to apply to spigots and
their distributions only; we have no evidence regarding the ontogeny of the silk
glands themselves. To make the figures more easily understandable, each also has
a label of the form “Nc 2 ALS-4.” This means, e.g., Nuctenea cornuta , female,
anterior lateral spinneret, fourth instar. The sex of the earliest instars could not
be determined.

RESULTS

Nuctenea cornuta. — First instars have no functional spigots or fusules (Fig. 30).
Functional spinning structures first appear in second instars. Although second
instars have few fusules (Figs. 1, 7, 13), they have examples of all spigots except
CY (Table 1).

From second to fifth instars, two MAP occur on the mesal ALS margin, one
anterior and one posterior (Figs. 1, 5). In second and third instars those two
MAP are similar in size (Figs. 1, 2). In fourth and fifth instars the hind spigot
becomes smaller and finally atrophies to become the ALS MAP spigot “nubbin”
in the adult instar (Figs. 4-6).

The PMS mAP develop in a more complex pattern. Second instars have two
mAP spigots per PMS (Fig. 7). The posterior spigot apparently disappears in the
third and leaves a vestigial “nubbin” in its place (Fig. 8). The posterior position
of the nubbin is evidence that it is indeed the posterior mAP spigot that is lost.
Third instars also apparently replace the mAP spigot represented by the nubbin
with a new mAP spigot between the anterior one and the posterior nubbin. In
effect the posterior mAP spigot has “changed places” and left a scar in the old
position. The new mAP spigot is generally smaller than the old one. The size
differences are clear in fourth and fifth instars (Figs. 9-11). This new mAP spigot,
which first appeared in the third instar, also disappears by the adult instar and
leaves its own vestigial nubbin on the posterior PMS margin (Fig. 12). In all, 3
mAP appear on the PMS during development but two are lost. Only the most
anterior, which first appeared in the second instar, persists as a functional spigot
in the adult instar.

One could also interpret the nubbin that appears in the fifth and sixth instars
(Figs. 11, 12) as the same, persistent nubbin. This would imply that the second
mAP spigot of the fifth instar is lost in the adult instar without a trace, and
would therefore propose yet a third method of spigot or fusule renewal. We
prefer to think that the nubbin in the adult instar is the scar of the posterior
spigot present in the fifth, because then the overall hypothesis for how spiders
renew spinning structures remains (relatively) simple.

A small, presumably non-functional PMS CY spigot is first visible in the
fourth instar female (Fig. 9), two molts before maturity in the sixth instar.

The development of AG and FL spigots is more stable. They also first appear
in the second instar (Fig. 13), as usual grouped in a triad. Once present they
never atrophy or leave nubbins (except in adult males), and their number remains
the same (Figs. 14-18). They are apparently molted in situ like any normal

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Figures 1-6. — Nuctenea cornuta ALS spinneret ontogeny (anterior up): 1, second instar, showing
two MAP at left, PI group at right; 2, third instar, note first appearance of tartipores in PI field; 3,
fourth instar; 4, fourth instar, male; 5, fifth instar; 6, adult instar, note single MAP spigot and
adjacent nubbin.

appendage. They function throughout the ontogeny. Aciniform spigots on the
PLS increase in number, and at least from the 4th instar onwards, also show
tartipores (Fig. 15-18). Two CY spigots appear in the fourth instar female, two
molts before maturity (Figs. 15, 18).

Table 1 shows the number of fusules per spinneret in each instar. Total fusule
complement, derived by doubling the counts in Table 1 and neglecting variation

YU & CODDINGTON— ONTOGENETIC CHANGES IN SPINNING FIELDS

335

Figures 7-12. — Nuctenea cornuta PMS spinneret ontogeny (anterior at left): 7, second instar,
showing two mAP at right, two AC at left; 8, third instar, showing two mAP at right with adjacent
nubbin, and three AC at left; 9, fourth instar (note appearance of single small CY spigot); 10, fourth
instar, male; 11, fifth instar; 12, adult instar, note appearance of mature CY spigot and disappearance
of one mAP spigot.

among individuals, is stable in the second instar; 16 ALS piriform, 4 PMS
aciniform and 6 PLS aciniform. The variability in the fusule number in 2nd, 3rd,
and 4th instars is small and earlier instars show less variation. Fusules on each
spinneret increase so that each successive instar has more fusules than the
previous one. Excluding the gain from first to second instar, fourth and sixth
instars gain relatively more fusules.

One of the two fourth instar specimens examined was male, so that immatures
of each sex could be compared as (Figs. 3 and 4; 9 and 10; 15 and 16). Total
number of fusules was 172 for the young male and 169 for the young female.
Differences in the number of aciniform and piriform fusules in the two sexes are

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Figures 13-18. — Nuctenea cornuta PLS spinneret ontogeny (anterior up): 13, second instar, showing
triad of two AG and one FL spigots below, and three AC spigots above; 14, third instar; 15, fourth
instar, note tartipores in AC field and two small CY spigots; 16, fourth instar, male; 17, fifth instar;
18, adult instar, note appearance of two large CY spigots at left.

also small. Evidently males and females do not differ greatly in spinning
complements before maturity, although females have CY spigots as early as the
fourth instar.

The ontogeny of ALS piriform fusules is special. From the third instar onward,
tartipores are found near normal piriforms. The form of the tartipores roughly
resembles the vestigial trace left by the lost MAP spigots (Figs. 2-6, 36). We

YU & CODDINGTON— ONTOGENETIC CHANGES IN SPINNING FIELDS

337

Table 1. — Number of spigots, fusules, and nubbins on each side of the spinning field in each instar
of species studied. A range of values reports variation within or among individuals.

{n)

MAP

mAP

tart.

PMS-

PLS-

N. cornuta

1st

(15)

2nd

( 4)

8-9

3rd

( 4)

15-17

5-7

7-8

4th

( 2)

41,47

20,24

7,10

27,29

5th

( 2)

61,74

26,27

12,15

42,43

6th (adult)

( 1)

110

7th (adult)

( 1)

124

TV. theisi

1st

( 4)

2nd

( 6)

5-9

3rd

( 4)

5-17

3-6

4-8

7-33

4th

( 3)

17-31

5-18

10-26

10-23

5th

( 3)

—

40-45

22-23

29-30

6th (adult)

( 2)

58,72

59,72

51,57

7th (adult)

( 2)

—

69,79

interpret these and other tartipores as vestiges left over from fusules functional in
the previous instar. If these tartipores are counted, interesting trends appear
(Table 1). In third, fourth and fifth instars, the range of tartipores present in an
instar is roughly equivalent to the range of piriform fusules in the previous instar.
The second instar PI persist only for this instar because their number (16-18) is
roughly equal to the number of tartipores in the third instar (10-14; difference
probably due to individual variation). A similar pattern of total replacement
probably also occurs in the third instar PI because their number (30-34) roughly
equals that of tartipores in fourth instars (40-48). However, we cannot be certain
that all fourth instar tartipores can be construed as remnants of third instar PI,
because it is possible, although unlikely, that some third instar tartipores persist
into the fourth instar. If they do, then some functional third instar PI fusules also
persist. The numbers are not exact. Judging from the iriAP spigot evidence,
however, nubbins themselves can disappear in the course of postembryonic
development (the nubbin of the first mAP spigot to atrophy is a example).
During young instars therefore, the entire complement of PI fusules may be
replaced at each molt.

The development of aciniforms is roughly the same, though not so regular. No
tartipores are found in third instars and relatively few are found in subsequent
instars. AC fusules apparently function and are molted in situ through more
molts than PI fusules. Nevertheless, the presence of sparse tartipores from at least
the fourth instar on suggests that some AC fusules do atrophy during
development, and are “replaced” by new fusules in new positions.

The distribution of ALS and PMS spigots and fusules remains more or less
constant during development. The PLS distribution changes the most from third
to fourth instars, when the spinneret tip and especially the AC spinning field
elongates (Figs. 14, 15). Fourth instar PLS already have the basic topography of
the adult.

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Figures 19-24. — Neoscona theisi ALS spinneret ontogeny (anterior up): 19, second instar, showing
two MAP at left, PI group at right; 20, third instar; note tartipores in PI field; 21, fourth instar; 22,
fifth instar, male; 23, adult instar, note single MAP and adjacent nubbin; 24, adult instar, different
individual.

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339

Figures 25-29. — Neoscona theisi PMS spinneret ontogeny (anterior up): 25, second instar, showing
two mAP below, two AC above; 26, third instar, showing two mAP below with adjacent nubbin, and
four AC above; 27, fourth instar; 28, fifth instar, male; 29, adult, note appearance of single CY spigot
and disappearance of one mAP spigot.

Figure 30. — Spinning field of first instar Nuctenea cornuta, note rudimentary morphology of
spinnerets and absence of functional spigots.

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Figures 31-35. — Neoscona theisi PLS spinneret ontogeny (anterior to the left): 31, second instar,
showing triad of two AG and one FL spigots at left, and three AC spigots at right; 32, third instar;
33, fourth instar, note tartipores in AC field; 34, fourth instar, male; 35, fifth instar.

Figure 36. — Closeup of Nuctenea cornuta fourth instar ALS, showing tartipores of pyriform
fusules.

YU & CODDINGTON— ONTOGENETIC CHANGES IN SPINNING FIELDS

341

Neoscona theisi. — The basic pattern of postembryonic growth of spinning
structures in this species is similar to N. cornuta , and so we only note features
that seem particularly significant. However, we illustrate N . theisi
comprehensively to emphasize that the patterns hold across these genera (Figs.
19-23; 25-35). This consistency argues that individual variation or interspecific
variation is unimportant at the level at which we are comparing patterns.

Again, spigots probably first appear in the second instar (Figs. 19, 25, 31).
Although all our preparations of first instars failed, this can be inferred from the
few spinning structures in second instars, a condition similar to second instar N.
cornuta (compare Figs. 1 and 19; 7 and 25; 13 and 31, numbers in Table 1).

Adult specimens have one MAP spigot and one mAP spigot with
accompanying nubbins as in N. cornuta (Figs. 23, 24, 29). One mAP spigot of the
second instar also atrophies by the third instar (Fig. 26). The same pattern may
occur in the ALS MAP spigot as well in N. theisi. If the ALS MAP area in third
instars is carefully examined, one possible nubbin can be observed at the inner
margin of the posterior MAP spigot (Fig. 20). Like the nubbin near third instar
PMS mAP spigot, this appears to be an atrophied MAP spigot which only
functioned during the second instar. From the MAP spigot distribution in second
and third instars we infer that the third instar posterior MAP spigot is new, and
so the nubbin came from the posterior MAP spigot in the second instar. This
new MAP spigot also atrophies by the sixth instar. Evidence for a similar process
of ALS MAP spigot replacement in third instars of N. cornuta is negative or
equivocal (Fig. 2).

Fusule number varies more within an instar in this species than in N. cornuta .
The instar in which the largest number of fusules is gained is difficult to
determine, because fusule number seems to increase evenly in each instar.

As in N. cornuta , the number of fusules in a fourth instar male and female are
very similar (Figs. 33, 34). The same holds true for other spinnerets (male, Figs.
22, 28; female not illustrated). Unlike N. cornuta , N . theisi fourth and fifth instar
females lack rudimentary CY spigots (Figs. 27, 33, 35).

Third instars have many ALS tartipores (Table 1 and Fig. 20). The number of
tartipores counted for N. theisi is not as accurate as that for N. cornuta because
piriforms in this species are too densely packed. Tartipores in third and fourth
instars can still be easily counted. In Table 1 tartipore numbers in one instar
match better fusule numbers in the previous instar than in N. cornuta.

The development of the shapes of spinning fields in N. theisi is almost the same
as that in N. cornuta except that the inner margin of the PLS of N. theisi are
more depressed and it is more difficult to see the whole spinning PLS field. The
biggest difference between the adults of the two species is PMS AC fusule
number. In N. cornuta , the PMS have the fewest fusules among three pairs of the
spinnerets, totalling only about 45 (Fig. 12). But N. theisi PMS AC fusules total
about 150 (Fig. 29).

DISCUSSION

The evidence presented here suggests two different modes in which these species
of spiders rejuvenate their spinning fields from one molt to the next. First, spigots
and or fusules can be simply molted in situ. Presumably these structures are

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replaced in the same way that spiders replace their exoskeleton with its associated
structures.

Second, an existing fusule or spigot may disappear from one instar to the next,
leaving behind a scar of the old spigot or fusule base (either tartipore or nubbin).
In the case of spigots, this mode of jettisoning old structures seems usually to be
accompanied by the appearance of a new spigot adjacent to the scar. This may
also be consistently the case for fusules, but the evidence is strong only for the
earliest instars.

Flagelliform and aggregate spigots may be unique in being rejuvenated
exclusively by the first mode. Piriform fusules in the third instar, and perhaps
subsequently, may be rejuvenated exclusively by the second mode. Aciniform
fusules, minor ampullate spigots, and perhaps the primary major ampullate spigot
apparently undergo both modes of replacement during their functional lives.

The appearance of CY spigots in N. cornuta two instars before maturity is
startling, as CY spigots typically appear only in adults (Kovoor 1987). We found
no trace of these spigots in N. theisi before the adult molt. Perhaps Nuctenea is
phylogenetically derived in this respect.

Because we did not attempt to describe the spinning complement of an
individual through successive molts but instead compared cohorts of individuals
from the same eggsac, the variation between individuals weakens the evidence for
some of these inferences. We can not be sure that piriforms fail to persist from
one molt ot the next, or that major ampullates are routinely replaced by the
second mode, i.e., the production of nubbins. Many spigots, as opposed to
fusules, do persist from one molt to the next.

Our interpretations also depend on the inference that the nubbins and
tartipores are in fact vestigial. To some extent, we are merely extending the
accepted explanation for spigot nubbins, at least in the case of the ALS major
ampullate spigot, to explain structures associated with fusules. These structures
have also been interpreted as sensory organs (‘’petits organes vraisemables
sensoriels,” Kovoor 1986, p. 19). Similar structures have been found in most
families of spiders excepting mesotheles (Shear et al. 1989). Our interpretation of
the PI and AC tartipores as vestigial scars of previous fusules is new. Sectioning
of the structures might decide the issue if one assumes that the enervation and
secretory connection to the old spigot should also be vestigial, if not absent
altogether. Because we did not section nubbins or tartipores, we cannot comment
on a possibly sensory role. Evidence at the cellular level on how the molting
process affects silk glands is also lacking.

If our inferences are correct, the second mode of renewal would seem to make
continuity of silk production through the molting process difficult. Appearance of
nubbins or tartipores implies either that the silk gland and duct serving that
structure also atrophies, or that the spider somehow connects the old system to
the new spigot or fusule in a rather short time. It would be interesting to know if
spiders cease using their piriform or aciniform glands in advance of a molt, and if
so, how long before. Which spigots make molting cells or chambers? If spiders do
switch the connection of ducts at the time of the molt, the process must be
complex. The other explanation-that they replace substantial numbers of
secretory systems at each molt-also seems somewhat bizarre.

In N. theisi and possibly N. cornuta one pair of MAP appears to atrophy in
the third instar, and another pair appears to compensate for the absent spigot,

YU & CODDINGTON— ONTOGENETIC CHANGES IN SPINNING FIELDS

343

thus restoring the status quo for juvenile araneoids. Replacement of one ALS
MAP spigot by another in juvenile instars has not been reported previously in
araneoid spiders.

Replacement of the ALS ampullate spigot in the third instar is rendered more
plausible by the obvious replacement of the ampullate that takes place on the
PMS. The ontogenetic patterns are similar. Surprisingly, three pairs of mAP
appear during development: two appear in the second instar and one at the third.
Two of these disappear before the adult stage. New spigots always seem to
emerge posterior to existing ones. This pattern may have been misunderstood by
Wasowska (1977) who reported that only one pair of mAP is atrophied before
maturity in Araneus diadematus Clerck. Perhaps A. diadematus shows a different
pattern.

Wasowska (1977) reported that spinning structures also appear in the “first”
instar in A. diadematus , but that AG and FL exist only from the “second” instar;
in Metellina segmentata (Clerck), spinning structures appear also in “first” instars.
Our results agree in part, because Wasowska numbered instars differently,
counting the first eclosed stage as first instar, whereas we count it as the second.
However, our results also differ in that we found all classes of spinning structures
on the second instar. The pattern we found makes more biological sense, because
second instars are fully equipped to make viscid catching webs.

The increase in number of PI and AC differs slightly between species. In N.
cornuta fourth and sixth instars gain the most, but in N. theisi the gain between
instars is more or less the same. Wasowska (1977) reported that all species studied
by her gained the most at the third instar. Our results again differ. Opell (1982)
found that the number of fusules in the cribellum of Hyptiotes cavatus (Hentz)
increased most from the third to fourth, and evenly from the fourth to the sixth
instar. This is similar to the ontogeny of N. theisi. The gain in number of fusules
probably differs between taxa; only more studies will resolve the issue.

Based on the results both from this study and existing papers (Mikulska 1966;
Wasowska 1977), all araneid adults examined thus far (and all araneoids) have
only one functional pair of ALS MAP spigots, whereas they have two pairs of
MAP in some earlier instars. On the other hand, Metellina segmentata has two
pairs of MAP only in “first” instars; the other four instars have just one pair of
MAP (Wasowska 1977). Metellina segmentata MAP spigot ontogeny thus seems
accelerated relative to the rest of the spinning structures. If true of other
tetragnathids, this ontogenetic pattern supports the inference that metines and
other tetragnathids are derived araneoids rather than primitive (Coddington 1986,
1989).

The ontogeny of mAP is further evidence for the same inference. According to
Wasowska (1977), Metellina segmentata and Enoplognatha ovata (Clerck) both
have just a single mAP during juvenile instars, as opposed to the two mAP
characteristic of araneids. By ontogenetic criteria the araneid condition is
primitive and thus this evidence confirms both theridiids and tetragnathids as
derived ananeoids relative to araneids (Coddington 1989, 1990).

ALS MAP nubbins near the functional MAP are also found in adult uloborids
and in Deinopis (the latter have numerous ALS MAP). These nubbins apparently
reflect MAP existing in younger instars (Coddington 1989). Both deinopoids and
araneoids seem to lose the posterior member of the pair. Deinopoids, araneoids

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and possibly some dictynids are unique as far as we know in having persistent
ALS MAP nubbin(s) in the adult stage (Coddington in press).

ACKNOWLEDGMENTS

We are greatly indebted to the following persons who gave much help in the
course of this study: Scott Larcher with specimen preparations, SEM scanning
and darkroom work; Walter Brown, Brian Kahn and Suzanne Brown with
specimen coating, negative developing and SEM technique. We also thank
Jacqueline Palmer, Jacqueline Kovoor, Charles Griswold, Herbert Levi, and
Brent Opell for comments on the manuscript. Edward Tillinghast and Mark
Townley first discovered cylindrical spigots in juvenile araneid females and
pointed them out in our SEM scans. We thank them for permitting us to use that
information in advance of their own publication. The Smithsonian Institution
provided a Graduate Student Fellowship to the first author. However, we would
like to give our special thanks to Prof. Jingzhao Zhao who kindly provided all
the specimens for this work as well as all the information about their
developmental stages. Without his help this study would not have been possible.

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Coddington, J. A. 1986. The monophyletic origin of the orb web. Pp. 319-363, In Spiders: Webs,
Behavior, and Evolution. (W. A. Shear, ed.). Stanford Univ. Press, Stanford, California.

Coddington, J. A. 1989. Spinneret silk spigot morphology, evidence for the monophyly of orb
weaving spiders, Cyrtophorinae (Araneidae), and the group Theridiidae and Nesticidae. J.
Arachnol. 17(1):7 1-95.

Coddington, J. A. 1990. Ontogeny and Homology in the Male Palpus of Orb Weaving Spiders and
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Coddington, J. A. In press. Cladistics and spider classification: Araneomorph phylogeny and the
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Glatz, L. 1967. Zur Biologic und Morphologie Von Oecohius annulipes Lucas (Araneae, Oecobiidae).
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Glatz, W. 1972. Der Spinnapparat hapiogyner Spinnen (Arachnida, Araneae). Z. Morph. Tiere, 72:1-
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Glatz, W. 1973. Der Spinnapparat der Orthognatha (Arachnida, Araneae). Z. Morph. Tiere, 75:1-50.
Kokocinski, W. 1968. Etude biometrique de la croissance des filieres au cours de developpement post-
embryonnaire chez l’araignee Agelena lahyrinthica (Clerck) (Araneae, Agelenidae). St. Soc. Sc.
Tor., S.E. Torun, 8(6): 1-81.

Kovoor, J. 1986. Lap pared sericigene dans les genres Nephila Leach et Nephilengys Koch: anatomie
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Kovoor, J. 1987. Comparative structure and histochemistry of silk-producing organs in arachnids. Pp.

160-186, In Ecophysiology of Spiders. (W. Nentwig, ed.). Springer-Verlag, Berlin.

Mikulska, I. 1966. The spinning structures on the spinnerets (thelae) of Nephila davipes (LA Zool.
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Mikulska, I. 1967. The external spinning structures on the thelae of the Argiope aurantia Lucas. Zool.
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Mikulska, I. 1969. Variability of the number of external spinning structures in female spiders
Cluhiona phragmitis C. L. Koch in populations to various degrees isolated. Zool. Pol, 1 9(2):279-
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Opell, B. D. 1982. Cribellum, calamistrum and ventral comb ontogeny in Hyptiotes cavatus (Hentz)
(Araneae: Uloboridae). J. Arachnol., 5(8):338-343.

Peters, H. M. 1983. Struktur and Herstellung der Fangfaden cribellater Spinnen (Arachnida:

Araneae). Verh. Naturw. Ver. Hamburg, 26:241=253.

Peters, H. M. 1984. The spinning apparatus of Uloboridae in relation to the structure and
construction of capture threads (Arachnida, Araneae). Zoomorphology, 104(2):96- 1 04.

Peters, H. M. and J. Kovoor. 1980. Un complement a Fappareil sericigene des Uloboridae (Araneae):

le paracribellum et ses glandes. Zoomorphology, 96(1 -2):9 1-102.

Richter, C. 1970a. Morphology and function of the spinning apparatus of the wolf spider Pardosa
amentata (Cl.) (Araneae, Lycosidae). Z. Morph. Tiere, 68:37-68.

Richter, C. 1970b. Relation between habitat structure and development of the glandulae ampullaceae
in eight wolf spider species ( Pardosa , Araneae, Lycosidae). Oecologia (fieri.), 5:185-199..

Shear, W.A., J. M. Palmer, J. A. Coddington and P. M. Bonamo. 1989. A Devonian spinneret; early
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Wasowska, S. 1966. Comparative morphology of the spinning fields in females of some spider species.
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Wasowska, S. 1967. The variability of the number of external spinning structures in female spider of
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Wasowska, S. 1970. Structures fileuses exterieures sur les filieres (thelae) de 1’araignee Argiope
bruennichi (Scopoli). Zool. Pol., 20:257-2268.

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population of Aranea sclopetarius Clerck. Zool. Pol., 23:109-1 18.

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Manuscript received February 1990, revised May 1990.

Cangialosi, K. R. 1990. Life cycle and behavior of the kleptoparasitic spider, Argyrodes ululans
(Araneae, Theridiidae). J. ArachnoL, 18:347-358.

LIFE CYCLE AND BEHAVIOR
OF THE KLEPTOPARASITIC SPIDER,
ARGYRODES ULULANS (ARANEAE, THERIDIIDAE)

Karen R. Cangialosi

Department of Zoology
Miami University
Oxford, Ohio 45056 USA

ABSTRACT

This study investigated the life cycle and behavior of Argyrodes ululans which is a specialist
kleptoparasite in the communal webs of its social spider host, Aneiosimus eximius. Observations of
natural and enclosed colonies of An. eximius revealed that large An. eximius colonies maintain steady
populations of high numbers of differently aged Ar. ululans individuals whereas small colonies contain
fewer kleptoparasites less predictably. Adult female Ar. ululans forage almost exclusively by stealing
newly captured prey directly from their hosts and were never observed to prey on host spiders.
Although male and juvenile Ar. ululans will sometimes steal prey from An. eximius , they tend to
scavenge more and feed on prey scraps abandoned by their hosts.

INTRODUCTION

Spiders in the genus Argyrodes conduct nearly all of their activities in the webs
of other spiders rather than building webs of their own (Exline and Levi 1962;
Gertsch 1979). Argyrodes can exist in a variety of relationships with their host
spiders (as commensals, kleptoparasites, predators) depending on factors such as
relative size of host and Argyrodes , morphology of host web, and host feeding
rate (Wise 1982; Larcher and Wise 1985). Although specific relationships for
certain Argyrodes- host systems have been determined (Exline and Levi 1962;
Smith Trail 1980; Tanaka 1984; Larcher and Wise 1985), the life cycle and
foraging behavior of only a few Argyrodes species have been studied in any detail
(Vollrath 1979, 1987; Larcher and Wise 1985; Whitehouse 1986).

Argyrodes ululans Cambridge is a specialist kleptoparasite in the communal
webs of its host, Aneiosimus eximius Simon, which lives in the undergrowth of
tropical rainforests in Peru. In this paper I describe some aspects of the natural
history and behavior of Argyrodes ululans , including its relative abundance in
Aneiosimus eximius colonies, general activity, reproductive behavior, and
foraging behavior. Comparisons are drawn with other Argyrodes species that
have solitary and/or temperate-zone hosts.

METHODS

This research was conducted in the Tambopata Reserved Zone, 35 km
southwest of Puerto Maldonado, Madre de Dios, Peru. The reserve is located

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within a region of subtropical moist forest described in detail elsewhere (Erwin
1985).

Anelosimus eximius , a highly social spider, is common in this area. These
spiders build large communal webs usually within understory vegetation. The
webs consist of a dense bowl-shaped sheet or capture surface from which strands
of tangled silk extend upward, sometimes for several meters, to form a barrier.
Dead leaves and other debris are incorporated into the bowl of the web as
retreats. The barrier is less visible to insects and is used to ensnare prey. Colonies
at Tambopata average 68.86 cm ± 50.28 cm (range 10-290 cm) in length (the
longest dimension of the three-dimensional bowl) and contain from 5 to
approximately 2,500 spiders (Rypstra, unpublished data), most of which are
female as in other colonies of this species (Aviles 1986; Vollrath 1986).
Anelosimus eximius individuals cooperate in prey catpture, feeding, colony
construction, web maintenance, and care of young (Christenson 1984; Vollrath
and Rohde-Arndt 1983).

The barrier webbing of An. eximius colonies frequently houses a
kleptoparasite, Argyrodes ululans , that specializes in stealing prey from its social
host. Ar. ululans spends its entire life cycle within the barrier portion of An.
eximius webs where it forages, mates, and lays egg sacs.

Surveys of colonies. — Anelosimus eximius colony length and the number of
Argyrodes ululans individuals inhabiting the colonies were determined
approximately every month. I recorded the total number of female, male, and
juvenile kleptoparasites within each colony. For two of the colonies (#883 and
#885), these data were collected every one to two weeks from September 1 to
November 10, 1988.

General activity. — The activity of individual kleptoparasites (adult females,
adult males, and juveniles) was monitored for periods of 1 to 4 hours between
0600 and 2300 for a total of 125 spider-hours (one spider observed for 1 hour).
Approximately 30-40 individual kleptoparasites in six different natural colonies
were observed. Data were collected from August 26 to November 10, 1988.

Mating and reproduction. — Natural colonies: During observations of general
activity and stealing behavior, 19 matings were observed. I recorded the details of
the courtship behavior and the duration of copulation. Some life history and
reproductive characteristics of four female Argyrodes ululans individuals in
natural colony #885 were recorded every day from September 1 to November 10,
1988. I recorded the date of molt from penultimate to adult, date first egg sac
was laid, date of hatching, and date second egg sac was laid. For each female I
recorded daily whether it was in an active state, inactive and gravid, or guarding
an egg sac.

Enclosed colonies: Female Ar. ululans that had laid egg sacs in enclosed
colonies of An. eximius (maintained in screened field enclosures, 30 X 30 X 30
cm, for use in other experiments, Cangialosi 1990b) were used for observations of
egg sac guarding behavior. Egg sacs were removed from two females in separate
cages and the reaction of each female was recorded. For one of the females, an
egg sac of a different female was placed in the cage with her 30 min after the
original one had been removed. This was done to see whether the female could
recognize her own egg sac and distinguish it from an egg sac of another female.

Foraging behavior. — Detailed observations of the foraging behavior (including
prey stealing) of Ar. ululans were recorded for adult females, adult males, and

CANGIALOSI— LIFE CYCLE OF ARGYRODES ULULANS

349

Figure 1. -Linear regression of total number of
Ar. ululans on An. eximius colony length (cm).
Equation for the line is y = —3.99 + 0.1 24x; R2 =
0.88.

juveniles foraging in natural colonies of An. eximius. Observations were made for
both naturally entering insects and those that were introduced purposely by
dropping or gently throwing them into the colonies.

RESULTS

Abundance of Argyrodes ululans. — Colonies of An. eximius contained from
zero to 24 individuals of Ar. ululans. The number of Ar. ululans per colony
increases with increasing host colony size (Fig. 1). The relative proportions of
females, males, and juveniles that comprise the total population of Ar. ululans
living within a colony is dependent upon the size of the colony and changes
during the course of a season (Fig. 2). In colony #885 (medium sized; 87-93 cm),
the number of juveniles decreased steadily from five to zero between September 1
and October 8 and remained at zero until an egg sac hatched on November 5
(Fig. 2a). The number of adult females and males in colony #885 remained
constant after the disappearance of the juveniles (from maturation or dispersal).
In colony #883, which was larger than #885 (175-188 cm), there was a consistently
high number of juveniles and the number of mature females increased from
September 1 to November 10 (Fig. 2b). Adult males remained relatively low in
comparison to the number of females in this colony.

General activity and behavior. — Eight behavioral activities of Ar. ululans were
recognized and recorded: (1) rotary probing (rotating the first pair of legs at the
coxatrochanter joint, Cangialosi 1990a); (2) feeding (extracting food from prey);
(3) folded (resting or inactive position in which the spider remains motionless in
the web with the legs folded up near the body, Fig. 3a); (4) still (also an inactive
state in which the spider sits in the web motionless with the legs outstretched,
Fig. 3b); (5) grooming (cleaning legs by passing them through the chelicerae); (6)
mating (courtship and copulation); (7) stealing behaviors (including leg waving,
web shaking, and clearing silk); and (8) walking (locomotion on the webbing).

Overall, the proportion of time allocated to the different categories of behavior
is not independent of the time of day for adult females (3X8 contingency table,
X2 = 80.78, P < 0.001), adult males (3X7 contingency table, x — 48.13, P <
0.001) or juveniles (3X7 contingency table, x2 = 140.98, P < 0.001). Females are
more likely to be in a folded rest state from 0600 to 1100 hours, feeding from
1101 to 1600, and in a still position from 1601 to 2300 (Fig. 4a). Males spend
most of their time in a still position but are less likely to do so from 0600 to 1100

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>20 >20

COLONY #885 (87-93cm)

, — i — i- v ■ — r —v — r t — r — i ■

Sept 1 Sept 17 S*x» Sec* 23 S*X27 0es3 Oct6 Oct I Oe 12 Oa 20 Oa 24 NovS Hot 10

DATE (1988)

Figure 2. — Total number of female, male, and juvenile Ar. ululans in An. eximius colonies for dates
in Sept and Nov, 1988. A, colony #885 (87-93 cm); B, colony #883 (175-180 cm).

(Fig. 4b). Rotary probing for males is more common from 0600 to 1100 and from
1601 to 2300 (Fig. 4b). No adult males were observed feeding during these
observations. For juveniles, a folded rest state is more likely from 0600 to 1100
and a still position is more common later in the day (Fig. 4c). Similar to adult
females, juveniles also spend most of their time feeding from 1101 to 1600 (Fig. 4c).

Mating and reproduction. — Compared to many other spider species, the
courtship behavior of Ar. ululans is relatively short and simple. Within the
barrier webbing of the An. eximius colony, a rotary probing male slowly
approaches a female until he almost contacts her. Unreceptive females drop or
walk away from the male. A receptive female also begins to rotary probe directly
facing the male. After just a few seconds, copulation commences and continues

CANGIALOSI— LIFE CYCLE OF ARGYRODES U LULA NS

351

Figure 3. — Diagrams of rest positions of Ar. ululans in An. eximius webbing. A, legs folded against
body, B, legs outstretched. (Drawings by Rebecca Ellis).

from 2 to 15 min (N = 19) until the pair breaks apart and the spiders resume
other activities. After separating, two of the males observed approached another
female and also mated with her.

The females observed in colony #885 took from 14 to 19 days to lay their first
egg sac after reaching maturity (Table 1). One of the females produced a second
egg sac 12 days after the first (Table 1). Two to four days before laying eggs,
gravid females assume an inactive folded position high in the An. eximius colony
barrier and do not forage. An adult female Ar. ululans suspends its egg case in
the barrier web at night and guards it until hatching. A guarding female spends
almost all of her time in a folded position near the egg sac. When it is threatened
by another spider or an insect approaching nearby, it becomes alert and shakes
the web and egg sac sharply, which causes the intruder to flee. Guarding females
only stray away from their egg sacs in order to drink water from the silk strands
within a 5-10 cm radius around the egg sac; they do not forage or feed. The
guarding/ hatching time for three of the females in colony #885 was 17 to 18 days
(Table 1). Mean hatching time (time since egg sac is first laid until the young
emerge; not guarded since females were removed from egg sacs placed in vials)
for egg sacs laid in the cages was 22.8 days (SD = 2.32, N = 6, range 20-27).

Female ^4r. ululans with egg sacs become active foragers only if the egg sac is
lost, or after the egg sac hatches. Female #3 in natural colony #885 lost its egg
sac 6 days after laying (cause unknown) and resumed foraging that same day.

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BEHAVIORAL ACTIVITIES

Figure 4. — General activity of Ar. ululans. Percentage of total observations of different behavioral
activities in three time periods, 0600-1100, 1101-1600, 1601-2300. RP = rotary probing; Feed =
feeding; Fold = folded position; Groom = grooming; Mate = mating; Steal = web shaking, silk
clearing, and leg waving; Still = still position; Walk = walking. A, adult females, B, adult males, C,
juveniles.

CANGIALOSI— LIFE CYCLE OF ARGYRODES ULULANS

353

Table 1. — Some life history characteristics for four female Ar. ululans individuals. Time units are
days, (a = egg sac lost).

Female

Penultimate
to adult

Maturation molt
to 1st egg sac

Guarding time
(hatching time)

Time to

2nd egg sac

—

After removing an egg sac from its owner (which was laid in a cage 3 days
earlier), the female immediately started to search for the egg sac, wandering
around the area rotary probing and moving further and further away from its
original position for 105 min until she became inactive (folded). This female did
not attempt to steal prey that day or the following day, but was successful in
stealing a prey item two days after the egg sac had been removed. Removing an
egg sac from a second female in another cage produced similar searching
behavior. For this second female, an egg sac laid by a different female was placed
in the cage in the vicinity of the original egg sac after 30 min of searching. The
female investigated the egg sac for 5 min, moving around it and touching it with
her first pair of legs. She then became inactive and folded near the egg sac. By
the next day, this female had attached this new egg sac to the colony webbing
and was guarding it in the usual way.

Foraging behavior. — Females: Ar. ululans females feed primarily by stealing
prey freshly captured by its host. It specializes in An. eximius webs as it was
never found in webs of any other spider species examined on the study site
including all located colonies (8 total) of two other Anelosimus species (pers.
observ.). A Peruvian arachnologist involved in making a comprehensive collection
of the spider fauna at the site examined virtually every spider web that could be
located for a month in 1987 and a month in 1988. This investigator found no Ar.
ululans in any of the spider webs (other than An. eximius) that she examined (D.
Silva pers. comm.).

The main sequence of events for stealing attempts by adult females is
summarized in Fig. 5. (The individual behaviors of the kleptoparasites and of An.
eximius are described in more detail in Cangialosi 1990a and Cangialosi 1990b).
A female Ar. ululans locates a prey item in the process of being captured by An.
eximius be detecting vibrations while rotary probing. The kleptoparasite
approaches the prey slowly and waits above it (10-15 cm) in a still position until
the prey is subdued by the social spiders. Once the prey is immobilized, the
kleptoparasite moves more quickly toward it, either leg waving or clearing silk,
and then starts web shaking. The relative frequency of these behaviors varies
depending on such factors as the number of host spiders involved and their
reaction (Cangialosi 1990a). Once the prey item is cleared of host spiders, the
kleptoparasite attaches the prey to itself via a silk line, and transports it up into
the barrier web to feed. Females were never observed killing an An. eximius
individual but were observed feeding on them on five occasions (two adult
females, one adult male, one juvenile) in natural colonies. In the cages, the host
spiders that were observed eaten by kleptoparasites were those that were
accidently killed from prey movements during prey capture (N = 3).

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Figure 5. — Ethogram of adult female Ar. ululans prey-stealing behavioral sequences.

Males : Adult males spend very little time feeding (Fig. 3). However, males were
observed attempting to steal prey six times in natural colonies. Males tend to
scavenge more, feeding on prey left in the web by the social spiders and do not
usually transport prey. Insects or pieces of insects that have been in the webs for
several hours have only a few (if any) host spiders still feeding on them. The
kleptoparasite may shake the web and prey to remove these hosts and then feed
on the prey without transporting it.

Juveniles : Younger juveniles of both sexes tend to forage similarly to adult
males. However, in addition to scavenging for abandoned prey, they sometimes
move in and feed with the host spiders on newly captured insects. The hosts
apparently do not detect these kleptoparasites since they are able to feed for long
periods of time. As they get older, female juveniles begin to behave more and
more like adult females and exhibit the same stealing behaviors. Even relatively
small, immature kleptoparasites can remove host spiders from prey by web
shaking.

CANGIALOSI— LIFE CYCLE OF ARGYRODES ULULANS

355

No Ar. ululans (of any age or sex) were observed capturing even the smallest
prey on their own. In fact, when an Ar. ululans individual approaches and
touches a still insect that begins to move when contacted, the kleptoparasite will
back away from it quickly. This sometimes alerts the host to the insect’s presence
and they will attempt to subdue it. Afterwards, the kleptoparasite may try to steal
the newly captured prey.

DISCUSSION

Abundance and age/sex structure. — Large colonies of Anelosimus eximius
harbor greater numbers of Argyrodes ululans than small colonies. Smith Trail
(1980) found a higher number of Argyrodes fictilium (Hentz) and Ar. baboquivari
Exline and Levi in communal groups of Philoponella oweni (Chamberlin)

compared to solitary P. oweni , and no more than one Argyrodes was ever found
in any solitary web. She presents evidence that suggests that this distribution is
due to the fact that Argyrodes encounter communal groups more often than
solitary webs, and that Argyrodes remain longer in communal groups, which
probably represent a large source of potential prey to these predatory species of
Argyrodes. Elgar (1989) found a significant positive correlation between

aggregation size of the orb-weaver, Nephila edulis Koch and the number of
kleptoparasites, Ar. antipodianus Cambridge per web (after correcting for N.
edulis body size). He demonstrated that spiders in aggregations suffered a higher
colonization rate of kleptoparasites than spiders in solitary webs, which could
explain the kleptoparasite distribution. However, webs of other solitary host
species often contain many Argyrodes individuals (Robinson and Robinson 1973;
Rypstra 1981; Wise 1982; Larcher and Wise 1985).

Although larger colonies of An. eximius may have higher kleptoparasite

immigration rates, the fact that Ar. ululans completes its entire life cycle within
host colonies means that new kleptoparasites are added as the older ones
reproduce. Larger stable colonies are inhabited by a greater number of

kleptoparasites of all ages and reproductive states, and kleptoparasite spiderlings
hatch from egg sacs fairly regularly. Hence, the proportion of juveniles in large
An. eximius colonies stays relatively constant over time, thus maintaining a
steady supply of kleptoparasites. In smaller colonies, which might contain a few
adult females for only a certain time period, the hatching of juveniles is more
sporadic. Thus the presence of kleptoparasites in these colonies is less consistent.
Several smaller to medium sized colonies (12-65 cm) often contain no Ar. ululans
at all.

Although some Ar. ululans offspring remain in the natal colony, many newly
hatched spiderlings disappear shortly (1-2 days) after emerging. Presumably, some
percentage of these aerially disperse to other colonies. It is unclear how random
dispersal results in the location of new host colonies. Older juveniles and adult
males also coccasionally show up in colonies that previously contained no
kleptoparasites. The mechanisms, frequency, and patterns of emmigration require
further investigation.

General activity. — Most spider species are predominately active either diurnally
or nocturnally but not both (Foelix 1982). Ar. ululans forages in both the day
and night and rests intermittantly. The activity of this kleptoparasite, not

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surprisingly, appears to be generally geared to its host which, unlike most spider
species, actively forages 24 hours a day (Rypstra unpublished data; pers. observ.).
Ar. elevatus is day-active and Ar. caudatus is night-active when they cohabit
Nephila clavipes webs (Vollrath 1976). Being active at different times, along with
other behavioral and physiological adaptations, allows them to exploit their host
in different ways (Vollrath 1976, 1987).

Differences in behavioral activity of Ar. ululans among the time periods were
mainly due to differences in behaviors not related to prey stealing such as
changing from a still to a folded position. The significance of these two rest states
is ambiguous. The legs-outstretched still position would seem to be more of an
alert state than the legs-folded position; however, Ar. ululans quickly switchs
from a folded position to active behaviors when responding to prey. Sex
differences in timing of behavior may be related to mating activity. Males spend
more time rotary probing (probably in search of mates) when females are less
likely to be feeding.

Mating and reproduction. — The mating behavior of Ar. ululans is very simple
and unritualized. Elaborate courtship displays by male spiders generally function
to suppress the females’ predatory behavior toward the males (Bristowe and
Locket 1926; Platnick 1971; Foelix 1982). Because Ar. ululans is non-predatory, it
is reasonable to assume that the lack of extensive courtship in these
kleptoparasites is due to the fact that males are not in danger of being eaten.

The cessation of foraging during egg sac guarding (17-27 days) implies that egg
predation pressure is very strong for Ar. ululans. Since foraging resumes within
hours of an egg sac being lost, it is important for the kleptoparasites to
immediately start gaining reserves to produce a new one. To this end, they
apparently undergo quick physiological changes from a fasting state (and from
relative inactivity) to an active feeding state. Also, the diligent searching behavior
for lost egg sacs indicates that female Ar. ululans are sensitive to the presence of
their egg sacs. This might imply that abandoned egg sacs have little chance of
surviving to the hatching stage.

An. eximius cleans its web regularly (pers. observ.; Ryypstra pers. comm.;
Vollrath and Rohde-Arndt 1983; Christenson 1984) and undoubtedly removes
unattended Ar. ululans egg sacs from their communal web. In spite of this, there
may be benefits for Ar. ululans associated with suspending their egg sacs in An.
eximius colonies. An. caudatus (Taczanowski) females place their egg sacs away
from host webs and guard them until the young hatch, whereas Ar. elevatus
(Taczanowski) leaves its egg sacs unattended in host webs (Vollrath 1987). The
behavior of the host and the nature of its web may determine, in part, the
placement and guarding of Argyrodes egg sacs. Additionally, Ar. elevatus
produces more egg sacs (with more eggs per sac) than Ar. caudatus (one every 5
days for Ar. elevatus compared to one every 30 days for Ar. caudatus, Vollrath
1987). Vollrath (1987) suggests that, because of these and other factors, Ar.
elevatus is a more V-selected’ species whereas Ar. caudatus is a more ‘K- selected’
species (Pianka 1970). In these respects (low egg sac output and tenacious
guarding), Ar. ululans is more similar to Ar. caudatus. This might indicate that
Ar. ululans also tends to be more ‘^-selected’, however other factors such as
generation time and mortality need to be considered.

Foraging behavior. — Ar. ululans is a host-specific kleptoparasite which takes a
substantial portion of its hosts’ prey (Cangialosi in press). Males and juveniles

CANGIALOSI— LIFE CYCLE OF ARGYRODES U LULA NS

357

tend to scavenge more and perhaps function as commensals rather than
kleptoparasites. Juvenile females switch to stealing newly captured prey directly
from their hosts as they age and therefore turn more kleptoparasitic.

Wise (1982) suggested that predation may be more important for temperate
Argyrodes whereas kleptoparasitism might be more important for tropical
Argyrodes. This conclusion was based mainly on the fact that most tropical host
spiders studied are large orb-weavers (Robinson and Robinson 1973; Rypstra
1981; Vollrath 1979) and that kleptoparasitism is more likely when the Argyrodes
is much smaller than its host, and predation is more likely when Argyrodes is
bigger than its host. The temperate Argyrodes species studied by Smith Trail
(1980) are large compared to their hosts and are primarily predators. Individual
adult female Ar. ululans and An. eximius are roughly equivalent in body size (5-9
mm) and adult ^4r. ululans are bigger than An. eximius juveniles (subordinate).
Nonetheless, Ar. ululans appears to be nearly exclusively kleptoparasitic. Because
it is social, groups of An. eximius make this host “bigger” than Ar. ululans (and
therefore defensively stronger, Cangialosi, 1990b) making kleptoparasitism more
likely than predation.

Although direct predation by Ar. ululans on An. eximius individuals was not
observed (even for individuals starved six days, Cangialosi 1990a), Ar. ululans
were occasionally observed feeding on their hosts. These may have been
individuals that were already dead and scavenged by the kleptoparasites. Other
Argyrodes species have been observed to kill and/or feed on An. eximius
(Rypstra, unpublished data; Vollrath 1982). Tanaka (1984) found that Argyrodes
fissifrons O. R-Cambridge (which is much smaller than its hosts) preys on its
hosts when they are molting and therefore motionless. Because Ar. ululans does
not kill its host, capture its own prey, or cannibalize its mates, it would be
interesting to investigate whether they have venom which is capable of
immobilizing prey.

ACKNOWLEDGMENTS

This work was completed in partial fulfilment of the requirements for the
Ph.D. degree by K. R. Cangialosi in the Department of Zoology at Miami
University, Oxford, OH. Support for this research was derived from the following
sources: National Science Foundation grant BSR 86-04782 to A. L. Rypstra,
Sigma Xi, the Department of Zoology, Miami University, Oxford campus, and
the Hamilton campus of Miami University. I would like to thank Diana Silva for
identification of Argyrodes ululans ; voucher specimens are in the Javier Prado
Museum in Lima, Peru. I also thank the Ministerio de Agricultura in Lima, Peru
for providing collecting permits for this work. G. J. Binford, R. S. Tirey, and J.
Whitis provided helpful field assistance. I am grateful to D. H. Wise and F.
Vollrath for reading and improving the manuscript. I especially appreciate the
helpful and abundant advice of A. L. Rypstra in the field and on the manuscript.

LITERATURE CITED

Aviles, L. 1986. Sex ratio bias in the social spider Anelosimus eximius , with comments on the
possibility of group selection. Amer. Nat., 128:1-12.

358

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Bristowe, W. S. and G. H. Locket. 1926. The courtship of British lycosid spiders and its probable
significance. Proc. Zool. Soc. London, 2:317-347.

Cangialosi, K. R. 1990a. The behavioral and ecological interactions of the kleptoparasitic spider,
Argyrodes ululans, and its social spider host, Anelosimus eximius. Ph.D. dissertation, Miami
University. 120 pp.

Cangialosi, K. R. in press. Kleptoparasitism in colonies of the social spider, Anelosimus eximius
(Araneae: Theridiidae). Acta Zool. Fen.

Cangialosi, K. R. 1990b. Social spider defense against kleptoparasitism. Behav. Ecol. Sociobiol.,
27:49-54.

Christenson, T. E. 1984. Behaviour of colonial and solitary spiders of the theridiid species Anelosimus
eximius. Anim. Behav., 32:725-734.

Elgar, M. A. 1989. Kleptoparasitism: a cost of aggregating for an orb-weaving spider. Anim. Behav.,
37:1052-1054.

Erwin, T. L. 1985. Tambopata Reserved Zone, Madre de Dios, Peru: history and description of the
reserve. Rev. Per. Ent., 27:1-8.

Exline, H. and H. W. Levi. 1962. American spiders of the genus Argyrodes (Araneae, Theridiidae).
Bull. Mus. Comp. Zool. Harv., 127:75-204.

Foelix, R. F. 1982. Biology of Spiders. Harvard University Press, Cambridge.

Gertsch, W. J. 1979. American Spiders. Van Nostrand Reinhold Co., New York.

Larcher, S. R. and D. H. Wise. 1985. Experimental studies of the interactions between a web-invading
spider and two host species. J. Arachnol., 13:43-59.

Pianka, E. R. 1970. On r- and A'-selection. Amer. Nat., 104:592-597.

Platnick, N. 1971. The evolution of courtship behaviour in spiders. Bull. Brit. Arachnol. Soc., 2:40-47.

Robinson, M. H. and B. Robinson. 1973. Ecology and behavior of the giant wood spider Nephila
maculata (Fabricius) in New Guinea. Smiths. Cont. Zool., 149:1-76.

Rypstra, A. L. 1981. The effect of kleptoparasitism on prey consumption and web relocation in a
Peruvian population of the spider Nephila clavipes. Oikos, 37:179-182.

Smith Trail, D. S. 1980. Predation by Argyrodes (Theridiidae) on solitary and communal spiders.
Psyche, 87:349-355.

Tanaka, K. 1984. Rate of predation by a kleptoparasitic spider, Argyrodes fissifrons, upon a large
host spider, Agelena limbata (Araneae). J. Arachnol., 12:363-367.

Vollrath, F. 1976. Konkurrenzvermeidung bei tropischen kleptoparasitischen Haubennetzspinnen der
Gattung Argyrodes. Entomol. Germ., 3:104-108.

Vollrath, F. 1979. Behavior of the kleptoparasitic spider Argyrodes elevatus (Araneae, Theridiidae).
Anim. Behav., 27:515-521.

Vollrath, F. 1982. Colony foundation in a social spider. Z. Tierpsychol., 60:313-324.

Vollrath, F. 1987. Kleptobiosis in spiders. Pp 274-286, In Ecophysiology of Spiders. (W. Nentwig, ed.).
Springer-Verlag, Berlin, Heidelberg, New York, Tokyo.

Vollrath, F. and D. Rohde-Arndt. 1983. Prey capture and feeding in the communal spider Anelosimus
eximius. Z. Tierpsychol., 61:313-324.

Whitehouse, M. E. A. 1986. The foraging behaviours of Argyrodes antipodiana (Theridiidae), a
kleptoparasitic spider from New Zealand. New Zealand J. Zool., 13:151-168.

Wise, D. H. 1982. Predation by a commensal spider, Argyrodes trigonum, upon its host: An
experimental study. J. Arachnol., 10:1 1 1-1 16.

Manuscript received February 1990, revised May 1990.

1990. The Journal of Arachnology 18:359

RESEARCH NOTES

PREDATION ON THE GREEN TREEFROG
BY THE STAR-BELLIED ORB WEAVER,
ACANTHEPEIRA STELLATA (ARANEAE, ARANEIDAE)

Treefrogs are generally the predator and not the prey of spiders. McCormick
and Polis (1982) listed three instances of in which the reverse was true: a funnel-
web mygalomorph, Atrax formidabilis Rainbow; the araneid Nephila clavipes
(L.); and a pisaurid, Dolomedes okefenokensis Bishop.

On 12 August 1989 at ca. 0830 hours, I observed a female star-bellied orb
weaver spider, Acanthepeira stellata Walckenaer, feeding on the remains of a
green treefrog, Hyla cinerea. The predation occurred ca. 1.0 km north north-east
of Saucier, Harrison County, Mississippi. The spider was collected, along with its
prey, from the remnants of a web which was attached from the top of a
pokeweed ( Phytolacca americana) along a fenceline (ca. 1.5 m above the ground)
to an overhanging branch of a live oak ( Quercus virginiana ) which extended over
the fence.

The spider was collected while it was feeding upon the right lateral side of the
treefrog’s abdomen. Both spider and treefrog were preserved in 80% ETOH and
deposited in the author’s personal collection. Judging by the condition of the
treefrog, the capture was probably made during the previous night. The treefrog
had received two separate bites. Other than the abdominal feeding punctures, the
remaining bite was given to the dorsal area on the right thigh.

Measurements of spider and prey were made within 24 hours of collection. The
length of the spider was 15.5 mm. The treefrog measured 3.3 cm from snout to
vent. No dry weight was taken. No doubt the nearly two-fold difference in size
betwixt predator and prey was compensated by the web and venom of the
former.

LITERATURE CITED

McCormick, S. and G. A. Polis. 1982. Arthropods that prey on vertebrates. Biol. Rev., 57:29-58.
Timothy C. Lockley, P.O. Box 1481, Gulfport, Mississippi 39502 USA.

Manuscript received August 1989, revised April 1990.

1990. The Journal of Arachnology 18:360

SPIDERS (ARANEAE) IN THE DIET
OF AMERICAN WOODCOCK IN MAINE

Birds are recognized predators of spiders (Gertsch 1979; Kaston 1981).
Although numerous studies have reported spiders in avian diets, most concern
passerine species (e.g., Orians and Horn 1969; Cowie and Hinsley 1988; Guinan
and Sealy 1987) and few identify spiders to family or generic level. Information
on the taxa of spiders consumed by avian species will expand our knowledge of
bird-spider and predator-prey interactions.

The American woodcock ( Scolopax minor ) is a ground-dwelling bird that feeds
on invertebrates on and beneath the forest floor. Woodcock use their long bill to
extract prey from the soil and to capture prey on the surface (Sheldon 1967).
Quantitative analyses of woodcock food habits include spiders (Pettingill 1936;
Sperry 1940; Miller 1957; Krohn 1970), but the taxa consumed were not
identified. These studies also indicate that spiders compose a small percentage of
the biomass consumed by woodcock; however, a more recent analysis in Maine
suggests that spiders may be more important when the woodcock’s primary prey,
earthworms (Lumbricidae), are less available (Vander Haegen unpublished data).
This note documents the family, genus, and, in some cases, species of spiders
consumed by American woodcock collected on the Moosehorn National Wildlife
Refuge, Washington County, Maine.

Woodcock were collected from late March - late June, 1987-1989, either by
shotgun (N = 45), or as incidental mortalities from a radio-telemetry study ( N =
15). Immediately after shooting, 70% ethanol was forced down the esophagus to
retard digestion. Contents of the esophagus, proventriculus, and ventriculus were
removed and preserved in 70% ethanol. Contents were later submerged in a
shallow dish and examined with a stereomicroscope (10-60X). Spiders and spider
parts were removed and identified by the junior author. When genitalia were
present, specimens were identified to species based on keys and species
descriptions in Kaston (1981) and other consulted sources. In the absence of
spider genitalia, most parts could be identified only to order, family, and
sometimes genus. All spiders and spider parts were stored in 2-dram vials and will
be deposited in the arachnid collections of the U.S. National Museum of Natural
History, Washington, D.C.

Fifteen of 60 (25%) woodcock examined contained the remains of from 1 to 3
spiders. Spiders of 4 families, 5 genera, and at least 5 species were identified
(Table 1). Hunting spiders outnumbered web-spinning spiders 19 to 2; remains of
3 spiders were undetermined. Trochosa was the dominant genus among spider
prey found in woodcock digestive tracts. All of the identified genera except Coras
were also captured during expellant sampling of the sub-litter layer of woodcock
feeding habitats on the Refuge (Jennings et al. 1990).

The preponderance of hunting spiders eaten by woodcock was not reflected in
the results from expellant sampling, where web-spinning spiders outnumbered
hunters 2 to 1 (Jennings et al 1990). This suggests that woodcock either were
encountering a greater percentage of hunting vs. web-spinning spiders, or were
better able to detect and capture hunting vs. web-spinning spiders. Many of the
web-spinning species collected by expellant were small spiders of the families
Theridiidae, Linyphiidae, and Erigonidae. We suspect that such small spiders are

1990. The Journal of Arachnology 18:361

Table 1. — Species and number of spiders found in American woodcock stomachs, Moosehorn
National Wildlife Refuge, Washington County, Maine, 1987-89.

Family

Species

Number

Male

Female

Juv.

Agelenidae

Cicurina brevis (Emerton)

Coras sp.

Lycosidae

Trochosa terricola Thorell

Trochosa sp.

Clubionidae

Clubiona canadensis Emerton

Clubiona sp.

Thomisidae

Xysticus sp.

Undetermined

below the threshold of acceptable prey-size for woodcock. The stomach-content
results (Table 1) support this hypothesis because most of the spider prey eaten by
woodcock were Lycosidae, which generally are larger than species of theridiids,
linyphiids, and erigonids.

All identified genera eaten by woodcock were also captured during pitfall
trapping in spruce-fir forests of Maine (Hilburn and Jennings 1988; Jennings et
al. 1988). Hunting spiders, predominantly Lycosidae, were abundant in pitfall-
trap catches in Maine, a result attributable to the roving nature of this foraging
guild (Uetz and Unzicker 1976). The mobility of hunting spiders may also make
them more available to foraging woodcock. This study indicates that soil- and
litter-inhabiting spiders are included in the diet of American woodcock in Maine.

Portions of this research were supported by the U.S. Fish and Wildlife Service
through Research Work Order 14-16-0009-1557 No. 8, and the College of Forest
Resources, University of Maine. We thank Douglas Mullen and Greg Sepik,
Moosehorn National Wildlife Refuge, Calais, Maine, for logistical support. We
also thank Daniel McAuley, U.S. Fish and Wildlife Service, for help with
collecting woodcock. W. B. Krohn and A. M. Narahara provided helpful reviews
of the manuscript. This is contribution no. 1465 of the Maine Agricultural
Experiment Station.

LITERATURE CITED

Cowie, R. J. and S. A. Hinsley. 1988. Feeding ecology of great tits Parus major and blue tits Pams
caeruleus breeding in suburban gardens. J. Anim. Ecol, 57:611-626.

Gertsch, W. J. 1979. American Spiders. 2nd ed. Van Nostrand Reinhold Co., New York. 274 pp.

Guinan, D. M. and S. G. Sealy. 1987. Diet of house wrens, Troglodytes aedon and the abundance of
the invertebrate prey in the Dune Ridge Forest Delta Marsh, Manitoba, Canada. Canadian J.
Zool., 65:1587-1596.

Hilburn, D. J. and D. T. Jennings. 1988. Terricolous spiders (Araneae) of insecticide-treated spruce-fir
forests in west-central Maine. Great Lakes Entomol., 21:105-114.

Jennings, D. T., M. W. Houseweart, C. D. Dondale and J. H. Redner. 1988. Spiders (Araneae)
associated with strip-clearcut and dense spruce-fir forests of Maine. J. Arachnol., 16:55-70.

Jennings, D. T., W. M. Vander Haegen and A. M. Narahara. 1990. A sampling of forest-floor spiders
(Araneae) by expellant, Moosehorn National Wildlife Refuge, Maine. J. Arachnol., 18:173-193.

1990. The Journal of Arachnology 18:362

Kaston, B. J. 1981. Spiders of Connecticut. Revised ed. Bull. 70. State Geological and Natural
History Survey of Connecticut. 1020 pp.

Krohn, W. B. 1970. Woodcock feeding habits as related to summer field usage in central Maine. J.
Wildl. Manage., 34:769-775.

Miller, D. R. 1957. Soil types and earthworm abundance in woodcock habitat in central
Pennsylvania. M.S. Thesis, Pennsylvania State Univ., University Park. 69 pp.

Orians, G. H. and H. S. Horn. 1969. Overlap in foods and foraging of four species of blackbirds in
the potholes of central Washington. Ecology, 50:930-938.

Pettingill, O. S., Jr. 1936. The American Woodcock Philohela minor (Gmelin). Mem. Boston Soc.
Nat. Hist., 9:169-391.

Sheldon, W. G. 1967. The book of the American woodcock. Univ. Massachusetts Press, Amherst. 227

pp.

Sperry, C. C. 1940. Food habits of a group of shorebirds: Woodcock, snipe, knot, and dowitcher.
U.S. Biol. Survey Wildl. Res. Bull. 1. 37 pp.

Uetz, G. W. and J. D. Unzicker. 1976. Pitfall trapping in ecological studies of wandering spiders. J.
Arachnol., 3:101-111.

W. Matthew Vander Haegen, Maine Cooperative Fish and Wildlife Research
Unit, University of Maine, Orono, Maine 04469 USA, and Daniel T. Jennings,
Northeastern Forest Experiment Station, 180 Canfield Street, RO. Box 4360,
Morgantown, West Virginia 26505 USA.

Manuscript received, accepted May 1990.

IMBIBITION OF PRECIPITATED FOG
BY NAMIB DESERT SCORPIONS

The Namib Desert is one of the most arid areas on the planet, annually
receiving an average rainfall of 7-64 mm (coast to 110 km inland to the east;
Seely 1978). However, sections of the desert within —50 km of the coast of the
Atlantic Ocean are subject to periodic but heavy fogs. Fog precipitates on any
rise, e.g., rocks, plants and even animals.

On the morning of 13 August, 1989, a thick fog covered the Namib Desert
from the coast to at least as far inland as the Desert Ecological Research Unit of
Namibia at Gobabeb (60 km east of the coast). At 0800 hours, a large (> 80 mm
length) Parabuthus villosus (Peters) was observed 15 cm above the ground on
grass at Swartbank, —40 km SE of Walvis Bay. The temperature was 12-15° C;
consequently the scorpion was sluggish. It slowly moved its chelicerae over the
grass stems. Water covered these stems and it was obvious that the scorpion was
collecting and drinking water. We observed this behavior for 40 min before we
left.

Desert scorpions obtain water in a variety of ways. Some scorpions drink
surface water in the field (e.g., Centruroides exilicauda (Wood) [= C. sculpturatus
Ewing], Hadley 1990). This behavior also is often observed in the laboratory (W.
D. Sissom personal communication). Apparently many (most?) species never
drink but derive all their water directly from the hemolymph of their prey or via

1990. The Journal of Arachnology 18:363

water of metabolism (see Hadley 1990). This is the only report of a scorpion
using fog as a source of water.

Many Namib desert species imbibe precipitated fog (Seely 1978 for references).
Several species of tenebrionids are perhaps the best known fog drinkers. Some of
these beetles increase their catchment area by elevating their abdomens; some dig
trenches that trap fog (Seely and Hamilton 1976). Other Namib desert insects,
spiders, lizards and snakes are all known to drink fog. The observation that
scorpions also drink precipitated fog increases the taxonomic diversity of species
that practice such a behavior. This method of water acquisition is particularly
important in the coastal section of the Namib desert; rainfall decreases
monotonically from the east to west and the coastal section receives very little
rain (< 10 mm/ year). Conversely, fog precipitation decreases from west to east
until it is largely unimportant > 110 km inland. Up to 161 mm of fog water
precipitates annually near the coast.

We thank David Sissom and Michael Soleglad for making suggestions to
improve the manuscript.

LITERATURE CITED

Hadley, N. F. 1990. Environmental physiology. Pp. 321-340, In Biology of Scorpions, (G. A. Polis,
ed.). Stanford Univ. Press, Stanford, California.

Seely, M. K. 1978. The Namib dune desert: an unusual ecosystem. J. Arid Environ., 1:117-128.

Seely, M. K. and W. J. Hamilton. 1976. Fog catchment sand trenches constructed by tenebrionid

beetles, Lepidochora, from the Namib Desert. Science, 193:484-486.

Gary A. Polis, Department of Biology, Vanderbilt University, Nashville,
Tennessee 37235 USA; and Mary K. Seely, Desert Ecological Unit of Namibia,
P.O. Box 953, Walvis Bay 9190, SWA/Namibia.

Manuscript received March 1990, revised May 1990.

MATING BY FEMALE SCORPIONS
WHILE STILL CARRYING YOUNG

Mating and courtship behavior are reported for 29 species of scorpion in six of
the nine families of extant scorpions (Polis and Sissom 1990). However, recently
post-partum females from only a few species were reported to court during the
period (1-51 days) that they carry their newly born young (e.g., Centruroides,
Isometrus and Tityus spp). All these species are in the family Buthidae, a taxon
that is quite different in phylogeny, life history and behavior from scorpions in
the other eight families (Polis 1990; Sissom 1990). Here, we report a courtship by
Vaejovis eusthenura (Wood), a species of Vaejovidae in which a post-partum
female mated while still carrying her young.

1990. The Journal of Arachnology 18:364

The mating occured at 2330 hours on June 9, 1989 and was located 20 km east
of Cabo San Lucas, Baja California del Sur, Mexico. The male and female were
observed under ultraviolet light. When first observed, the male was leading the
female in the courtship dance (promenade) by grasping her pedipalp chelae
fingers with his own. She was carrying 14 first instars (only first instar scorpions
do not fluoresce under UV). This indicates that birth had occurred within 7-17
days, the period that vaejovids (9 species reported in the literature) are known to
spend before their first molt. The pair moved together for about 12 min before
the male deposited a spermatophore on a small rock. He subsequently pulled the
female over the spermatophore. She arched over and descended upon the
spermatophore, presumably aspirating the sperm into her gonopore. Thus the
mating was apparently successful. They separated immediately after the female
descended on the spermatophore (See Polis and Farley 1979, and Polis and
Sissom 1990 for a full description of courtship).

Since scorpions are iteroparous, courtship by post-partum females is not
surprising and has been reported previously for several species (Polis and Sissom
1990). However, courtship so soon after birth has not been reported for non-
buthid scorpions. Such behavior may be common but simply unobserved. This is
particularly plausible in sub-tropical and temperate scorpions because the general
periods of courtship (May through October in the northern hemisphere) and birth
(June through September) overlap. Nevertheless, the described behavior by recent
post-partum females is the first in approximately 40 observed courtship of
vaejovids ( Vaejovis , Vejovoidus, Paruro clonus), and Iurids ( Hadrurus ) that we
have observed in the field.

We thank David Sissom and Michael Soleglad for making suggestions to
improve the manuscript. D. Sissom kindly identified the courting pair.

LITERATURE CITED

Polis, G. A. 1990. Ecology. Pp. 247-293, In Biology of Scorpions. (G. A. Polis, ed.). Stanford Univ.
Press, Stanford, California.

Polis, G. A. and R. D. Farley. 1979. The ecology and behavior of mating in the cannibalistic
scorpion, Paruroctonus mesaensis Stahnke. J. Arachnol 7:33-46.

Polis, G. A. and W. D. Sissom. 1990. Life history, Pp. 161-223, In Biology of Scorpions. (G. A. Polis,
ed.). Stanford Univ. Press, Stanford, California.

Sissom, W. D. 1990. Systematics, biogeography and paleontology. Pp. 64-160, In Biology of
Scorpions. (G. A. Polis, ed.). Stanford Univ. Press, Stanford, California.

Gary A. Polis and Mark Mohnac, Department of Biology, Vanderbilt
University, Nashville, Tennesses 37235 USA.

Manuscript received March 1990, revised May 1990.

THE AMERICAN ARACHNOLOGICAL SOCIETY

President:

George W.Uetz (1989-1991)

Department of Biological Sciences
University of Cincinnati
Cincinnati, Ohio 45221

Membership Secretary:

Norman I. Platnick (appointed)

American Museum of Natural History
Central Park West at 79th Street
New York, New York 10024

Secretary:

James W. Berry (1989-1991)

Department of Biological Sciences
Butler University
Indianapolis, Indiana 46208

Directors:

Petra Sierwald (1989-1991), William A. Shear (1989-1991), Matthew H.
Greenstone (1990-1993).

Honorary Members:

P. Bonnet, W. J. Gertsch, H. Homann, H. W. Levi, G. H. Locket, A. F. Millidge,
M. Vachon, T. Yaginuma.

President-Elect:

Allen R. Brady (1989-1991)
Biology Department
Hope College
Holland, Michigan 49423

Treasurer:

Gail E. Stratton (1989-1991)
Department of Biology
Albion College
Albion, Michigan 49224

Archivist:

Vincent D. Roth

Box 136

Portal, Arizona 85632

CONTENTS

THE JOURNAL OF ARACHNOLOGY

VOLUME 18 Feature Articles NUMBER 3

Daily locomotor activity patterns in three species of Cupiennius
(Araneae, Ctenidae): The males are the wandering spiders,

Alain Schmitt, Martin Schuster and Friedrich G. Barth 249

Some aspects of the reproductive behavior of Lycosa tarentula
fasciiventris (Araneae, Lycosidae), C. Fernahdez-Montraveta

and J. Ortega 257

Determinants of fecundity in Frontinella pyramitela (Araneae,

Linyphiidae), Robert B. Suter 263

Potential lifetime fecundity and the factors affecting annual

fecundity in Urodacus armatus (Scorpiones, Scorpionidae), G. T. Smith 271

Courtship and mating behavior of Thelochoris karschi (Araneae,

Dipluridae), an African funnel web spider, Frederick A. Coyle and

Theresa C. O Shields 281

The amino acid composition of major ampullate gland silk (dragline)
of Nephila clavipes (Araneae, Tetragnathidae), Stephen J. Lombardi

and David L. Kaplan 297

Cooperative foraging for large prey by Paratemnus elongatus

(Pseudoscorpionida, Atemnidae), Jeanne A. Zeh and David W. Zeh 307

Allozyme variation in the introduced spider, Holocnemus pluchei
(Araneae, Pholcidae) in California, Adam H. Porter and

Elizabeth M. Jakob 313

Parasitism of Nephila clavipes (Araneae, Tetragnathidae) by an
ichneumonid (Hymenoptera, Polysphinctini) in Panama,

Ola M. Fincke , Linden Higgins and Edgar Rojas 321

Ontogenetic changes in the spinning fields of Nuctenea cornuta
and Neoscona theisi (Araneae, Araneidae), Liuming Yu and

Jonathan A. Coddington 331

Life cycle and behavior of the kleptoparasitic spider, Argyrodes ululans
(Araneae, Theridiidae), Karen R. Cangialosi 347

Research Notes

Predation on the green treefrog by the star-bellied orb weaver,

Acanthepeira stellata (Araneae, Araneidae), Timothy C. Lockley 359

Spiders (Araneae) in the diet of American woodcock in Maine, ^

W. Matthew Vander Haegen and Daniel T. Jennings 360

Imbibition of precipitated fog by Namib Desert Scorpions,

Gary A. Polis and Mary K. Seely 362

Mating by female scorpions while still carrying young, Gary A. Polis and
Mark Mohnac 363

Cover photograph, web of Philoponella vicina
(O. Pickard-Cambridge) (Uloboridae) by Jonathan A. Coddington
Printed by PrinTech, Lubbock, Texas, USA
Posted at Lubbock, Texas, 20 November 1990

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